ISSN 0253-2778

CN 34-1054/N

Open AccessOpen Access JUSTC Chemistry 31 October 2022

Regioselective synthesis of branched alkenylborons via copper-catalyzed protoborylation of 1,4-diynes

Cite this:
https://doi.org/10.52396/JUSTC-2022-0074
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  • Author Bio:

    Xinyue Sun is currently a master’s student in the Department of Chemistry under the supervision of Prof. Yunhe Xu at the University of Science and Technology of China. Her current research mainly focuses on organic synthetic chemistry

    Yunhe Xu is currently a Professor at the University of Science and Technology of China. His research interests include organosilicon chemistry and transition-metal-catalyzed C–H bond activation and functionalization

  • Corresponding author: E-mail: xyh0709@ustc.edu.cn
  • Received Date: 03 May 2022
  • Accepted Date: 07 June 2022
  • Available Online: 31 October 2022
  • A copper-catalyzed highly regioselective protoborylation of 1,4-diynes for the synthesis of alkenylboramide compounds was reported. Various (hetero)aryl and alkyl substituted terminal 1,4-diynes afforded the corresponding products in high yields and regioselectivities. The utility of alkenyl-B(dan) products was proven by their convenient derivatizations.
    Regioselective synthesis of branched alkenylborons via copper-catalyzed protoborylation of 1,4-diynes.
    A copper-catalyzed highly regioselective protoborylation of 1,4-diynes for the synthesis of alkenylboramide compounds was reported. Various (hetero)aryl and alkyl substituted terminal 1,4-diynes afforded the corresponding products in high yields and regioselectivities. The utility of alkenyl-B(dan) products was proven by their convenient derivatizations.
    • A copper-catalyzed protoborylation reaction of 1,4-diynes was developed.
    • The mono-phosphine ligand XPhos supported the formation of branched alkenylboron products in high yields and regioselectivities.
    • This reaction provides an efficient approach for the synthesis of multifunctionalized α-vinylborons.

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  • [1]
    Potgieter M, Wenteler G L, Drewes S E. Synthesis of rooperol [1, 5-bis(3’, 4’-dihydroxyphenyl)pent-l-en-4-yne]. Phytochemistry, 1988, 27: 1101–1104. doi: 10.1016/0031-9422(88)80282-6
    [2]
    Organ M G, Ghasemi H. Metal-catalyzed coupling reactions on an olefin template: the total synthesis of (13E, 15E, 18Z, 20Z)-1-hydroxypentacosa-13, 15, 18, 20-tetraen-11-yn-4-one 1-acetate. J. Org. Chem., 2004, 69: 695–700. doi: 10.1021/jo035376k
    [3]
    Arfaoui D E, Listunov D, Fabing I, et al. Identification of chiral alkenyl- and alkynylcarbinols as pharmacophores for potent cytotoxicity. Chem. Med. Chem., 2013, 8: 1779–1786. doi: 10.1002/cmdc.201300230
    [4]
    Li Y X, Xuan Q Q, Liu L, et al. A Pd(0)-catalyzed direct dehydrative coupling of terminal alkynes with allylic alcohols to access 1, 4-enynes. J. Am. Chem. Soc., 2013, 135: 12536–12539. doi: 10.1021/ja406025p
    [5]
    Shi X, Gorin D J, Toste F D. Synthesis of 2-cyclopentenones by gold(I)-catalyzed rautenstrauch rearrangement. J. Am. Chem. Soc., 2005, 127: 5802–5803. doi: 10.1021/ja051689g
    [6]
    Wu L J, Song R J, Luo S, et al. Palladium-catalyzed reductive [5+1] cycloaddition of 3-acetoxy-1, 4-enynes with CO: Access to phenols enabled by hydrosilanes. Angew. Chem. Int. Ed., 2018, 57: 13308–13302. doi: 10.1002/anie.201808388
    [7]
    Chen X, Baratay C A, Mark M E, et al. Gold and Brønsted acid catalyzed spirocyclization of 2- and 3-indolyl-tethered 1, 4-enyne acetates to spiro[4, n]alkyl[b]indoles. Org. Lett., 2020, 22: 2849–2853. doi: 10.1021/acs.orglett.0c00929
    [8]
    Blaszczyk S A, Glazier D A, Tang W. Rhodium-catalyzed (5 + 2) and (5 + 1) cycloadditions using 1, 4-enynes as five-carbon building blocks. Acc. Chem. Res., 2020, 53: 231–243. doi: 10.1021/acs.accounts.9b00477
    [9]
    Miyaura N, Suzuki A. Palladium-catalyzed cross-coupling reactions of organoboron compounds. Chem. Rev., 1995, 95: 2457–2483. doi: 10.1021/cr00039a007
    [10]
    Suzuki A. Recent advances in the cross-coupling reactions of organoboron derivatives with organic electrophiles, 1995–1998. J. Organomet. Chem., 1999, 576: 147–168. doi: 10.1016/S0022-328X(98)01055-9
    [11]
    Kotha S, Lahiri K, Kashinath D. Recent applications of the Suzuki–Miyaura cross-coupling reaction in organic synthesis. Tetrahedron, 2002, 58: 9633–9695. doi: 10.1016/S0040-4020(02)01188-2
    [12]
    Molander G A, Ellis N. Organotrifluoroborates: Protected Boronic acids that expand the versatility of the Suzuki coupling reaction. Acc. Chem. Res., 2007, 40: 275–286. doi: 10.1021/ar050199q
    [13]
    Tobisu M, Chatani N. Borreagentien für die orthogonale Funktionalisierung mithilfe von Suzuki-Miyaura-Kreuzkupplungen. Angew. Chem. Int. Ed., 2009, 121: 3617–3620. doi: 10.1002/ange.200900465
    [14]
    Lennox A J J, Lloyd-Jones G C. Selection of boron reagents for Suzuki–Miyaura coupling. Chem. Soc. Rev., 2014, 43: 412–443. doi: 10.1039/C3CS60197H
    [15]
    Zhang L, Lovinger G J, Edelstein E K, et al. Catalytic conjunctive cross-coupling enabled by metal-induced metallate rearrangement. Science, 2016, 351: 70–74. doi: 10.1126/science.aad6080
    [16]
    Tucker C E, Davidson J, Knochel P. Mild and stereoselective hydroborations of functionalized alkynes and alkenes using pinacolborane. J. Org. Chem., 1992, 57: 3482–3485. doi: 10.1021/jo00038a044
    [17]
    Miyaura N. Metal-catalyzed reactions of organoboronic acids and esters. Bull. Chem. Soc. Jpn., 2008, 81: 1535–1553. doi: 10.1246/bcsj.81.1535
    [18]
    Zhao M, Shan C C, Wang Z L, et al. Ligand-dependent-controlled copper-catalyzed regio- and stereoselective silaboration of alkynes. Org. Lett., 2019, 21: 6016–6020. doi: 10.1021/acs.orglett.9b02160
    [19]
    Bose S K, Mao L, Kuehn L, et al. First-row d block element-catalyzed carbon–boron bond formation and related processes. Chem. Rev., 2021, 121: 13238–13341. doi: 10.1021/acs.chemrev.1c00255
    [20]
    Alam S, Karim R, Khan A, et al. Copper-catalyzed preparation of alkenylboronates and arylboronates. Eur. J. Org. Chem., 2021, 2021: 6115–6160. doi: 10.1002/ejoc.202100817
    [21]
    Beletskaya I, Pelter A. Hydroborations catalysed by transition metal complexes. Tetrahedron, 1997, 53: 4957–5026. doi: 10.1016/S0040-4020(97)00001-X
    [22]
    Wang Y D, Kimball G, Prashad A S, et al. Zr-mediated hydroboration: stereoselective synthesis of vinyl boronic esters. Tetrahedron Lett., 2005, 46: 8777–8780. doi: 10.1016/j.tetlet.2005.10.031
    [23]
    Iwadate N, Suginome M. Synthesis of B-protected β-styrylboronic acids via iridium-catalyzed hydroboration of alkynes with 1, 8-naphthalenediaminatoborane leading to iterative synthesis of oligo(phenylenevinylene)s. Org. Lett., 2009, 11: 1899–1902. doi: 10.1021/ol9003096
    [24]
    Semba K, Fujihara T, Terao J, et al. Copper-catalyzed borylative transformations of non-polar carbon-carbon unsaturated compounds employing borylcopper as an active catalyst species. Tetrahedron, 2015, 71: 2183–2197. doi: 10.1016/j.tet.2015.02.027
    [25]
    Neeve E C, Geier S J, Mkhalid I A I, et al. Diboron(4) compounds: From structural curiosity to synthetic workhorse. Chem. Rev., 2016, 116: 9091–9161. doi: 10.1021/acs.chemrev.6b00193
    [26]
    Ojha D P, Prabhu K R. Pd-catalyzed hydroborylation of alkynes: A ligand controlled regioselectivity switch for the synthesis of α- or β-vinylboronates. Org. Lett., 2016, 18: 432–435. doi: 10.1021/acs.orglett.5b03416
    [27]
    Yoshida H. Borylation of alkynes under base/coinage metal catalysis: Some recent developments. ACS Catal., 2016, 6: 1799–1811. doi: 10.1021/acscatal.5b02973
    [28]
    Gunanathan C, Hölscher M, Pan F, et al. Ruthenium catalyzed hydroboration of terminal alkynes to Z-vinylboronates. J. Am. Chem. Soc., 2012, 134: 14349–14352. doi: 10.1021/ja307233p
    [29]
    Yamamoto K, Mohara Y, Mutoh Y, et al. Ruthenium-catalyzed (Z)-selective hydroboration of terminal alkynes with naphthalene-1, 8-diaminatoborane. J. Am. Chem. Soc., 2019, 141: 17042–17047. doi: 10.1021/jacs.9b06910
    [30]
    Obligacion J V, Neely J M, Yazdani A N, et al. Cobalt catalyzed Z-selective hydroboration of terminal alkynes and elucidation of the origin of selectivity. J. Am. Chem. Soc., 2015, 137: 5855–5858. doi: 10.1021/jacs.5b00936
    [31]
    Ben-Daat H, Rock C L, Flores M, et al. Hydroboration of alkynes and nitriles using an α-diimine cobalt hydride catalyst. Chem. Commun., 2017, 53: 7333–7336. doi: 10.1039/C7CC02281F
    [32]
    Zhang G, Li S, Wu J, et al. Highly efficient and selective hydroboration of terminal and internal alkynes catalysed by a cobalt (II) coordination polymer. Org. Chem. Front., 2019, 6: 3228–3233. doi: 10.1039/C9QO00834A
    [33]
    Chen J, Shen X, Lu Z. Cobalt-catalyzed Markovnikov-type selective hydroboration of terminal alkynes. Angew. Chem. Int. Ed., 2021, 60: 690–694. doi: 10.1002/anie.202012164
    [34]
    Pereira S, Srebnik M. A study of hydroboration of alkenes and alkynes with pinacolborane catalyzed by transition metals. Tetrahedron Lett., 1996, 37: 3283–3286. doi: 10.1016/0040-4039(96)00576-X
    [35]
    Ohmura T, Yamamoto Y, Miyaura N. Rhodium- or Iridium-catalyzed trans-hydroboration of terminal alkynes, giving (Z)-1-alkenylboron compounds. J. Am. Chem. Soc., 2000, 122: 4990–4991. doi: 10.1021/ja0002823
    [36]
    Lee T, Baik C, Jung I, et al. Stereoselective hydroboration of diynes and triyne to give products containing multiple vinylene bridges:   A versatile application to fluorescent dyes and light-emitting copolymers. Organometallics, 2004, 23: 4569–4575. doi: 10.1021/om049832m
    [37]
    Lyu Y, Toriumi N, Iwasawa N. (Z)-Selective hydroboration of terminal alkynes catalyzed by a PSP–pincer rhodium complex. Org. Lett., 2021, 23: 9262–9266. doi: 10.1021/acs.orglett.1c03606
    [38]
    Takahashi K, Ishiyama T, Miyaura N. A borylcopper species generated from bis(pinacolato)diboron and its additions to α, β-unsaturated carbonyl compounds and terminal alkynes. J. Organomet. Chem., 2001, 625: 47–53. doi: 10.1016/S0022-328X(00)00826-3
    [39]
    Jang H, Zhugralin A R, Lee Y, et al. Highly selective methods for synthesis of internal (α-) vinylboronates through efficient NHC–Cu-catalyzed hydroboration of terminal alkynes. Utility in chemical synthesis and mechanistic basis for selectivity. J. Am. Chem. Soc., 2011, 133: 7859–7871. doi: 10.1021/ja2007643
    [40]
    Moure A L, Mauleón P, Arrayás R G, et al. Formal regiocontrolled hydroboration of unbiased internal alkynes via borylation/allylic alkylation of terminal alkynes. Org. Lett., 2013, 15: 2054–2057. doi: 10.1021/ol4007663
    [41]
    Yoshida H, Takemoto Y, Takaki K. A masked diboron in Cu-catalysed borylation reaction: highly regioselective formal hydroboration of alkynes for synthesis of branched alkenylborons. Chem. Commun., 2014, 50: 8299–8302. doi: 10.1039/C4CC01757A
    [42]
    Zhang P, Suárez J M, Driant T, et al. Cyclodextrin cavity-induced mechanistic switch in copper-catalyzed hydroboration. Angew. Chem. Int. Ed., 2017, 56: 10821–10825. doi: 10.1002/anie.201705303
    [43]
    Gao Y, Yazdani S, Kendrick IV A, et al. Cyclic (alkyl)(amino)carbene ligands enable Cu-catalyzed Markovnikov protoboration and protosilylation of terminal alkynes: A versatile portal to functionalized alkenes. Angew. Chem. Int. Ed., 2021, 60: 19871–19878. doi: 10.1002/anie.202106107
    [44]
    Tsushima T, Tanaka H, Nakanishi K, et al. Origins of internal regioselectivity in copper-catalyzed borylation of terminal alkynes. ACS Catal., 2021, 11: 14381–14387. doi: 10.1021/acscatal.1c04244
    [45]
    Chen J, Gao S, Gorden J D, et al. Stereoselective syntheses of γ-boryl substituted syn-β-alkoxy- and syn-β-amino-homoallylic alcohols via a regio- and stereoselective allene diboration and aldehyde allylboration reaction sequence. Org. Lett., 2019, 21: 4638–4641. doi: 10.1021/acs.orglett.9b01535
    [46]
    Caspers L D, Finkbeiner P, Nachtsheim B J. Direct electrophilic C−H alkynylation of unprotected 2-vinylanilines. Chem. Eur. J., 2017, 23: 2748–2752. doi: 10.1002/chem.201606026
    [47]
    Sato T, Onuma T, Nakamura I, et al. Platinum-catalyzed cycloisomerization of 1, 4-enynes via 1, 2-alkenyl rearrangement. Org. Lett., 2011, 13: 4992–4995. doi: 10.1021/ol202104c
  • 加载中

Catalog

    1.  Copper-catalyzed borylation reactions.

    2.  Substrate scope of 1,4-diynes.a

    3.  Optimization of the reaction conditions for the synthesis of enantioenriched alkenylboron compound 3a'.

    4.  Gram-scale synthesis of alkenylboron product 3a.

    5.  Transformation of alkenylboron product 3a.

    6.  Proposed mechanistic pathway.

    [1]
    Potgieter M, Wenteler G L, Drewes S E. Synthesis of rooperol [1, 5-bis(3’, 4’-dihydroxyphenyl)pent-l-en-4-yne]. Phytochemistry, 1988, 27: 1101–1104. doi: 10.1016/0031-9422(88)80282-6
    [2]
    Organ M G, Ghasemi H. Metal-catalyzed coupling reactions on an olefin template: the total synthesis of (13E, 15E, 18Z, 20Z)-1-hydroxypentacosa-13, 15, 18, 20-tetraen-11-yn-4-one 1-acetate. J. Org. Chem., 2004, 69: 695–700. doi: 10.1021/jo035376k
    [3]
    Arfaoui D E, Listunov D, Fabing I, et al. Identification of chiral alkenyl- and alkynylcarbinols as pharmacophores for potent cytotoxicity. Chem. Med. Chem., 2013, 8: 1779–1786. doi: 10.1002/cmdc.201300230
    [4]
    Li Y X, Xuan Q Q, Liu L, et al. A Pd(0)-catalyzed direct dehydrative coupling of terminal alkynes with allylic alcohols to access 1, 4-enynes. J. Am. Chem. Soc., 2013, 135: 12536–12539. doi: 10.1021/ja406025p
    [5]
    Shi X, Gorin D J, Toste F D. Synthesis of 2-cyclopentenones by gold(I)-catalyzed rautenstrauch rearrangement. J. Am. Chem. Soc., 2005, 127: 5802–5803. doi: 10.1021/ja051689g
    [6]
    Wu L J, Song R J, Luo S, et al. Palladium-catalyzed reductive [5+1] cycloaddition of 3-acetoxy-1, 4-enynes with CO: Access to phenols enabled by hydrosilanes. Angew. Chem. Int. Ed., 2018, 57: 13308–13302. doi: 10.1002/anie.201808388
    [7]
    Chen X, Baratay C A, Mark M E, et al. Gold and Brønsted acid catalyzed spirocyclization of 2- and 3-indolyl-tethered 1, 4-enyne acetates to spiro[4, n]alkyl[b]indoles. Org. Lett., 2020, 22: 2849–2853. doi: 10.1021/acs.orglett.0c00929
    [8]
    Blaszczyk S A, Glazier D A, Tang W. Rhodium-catalyzed (5 + 2) and (5 + 1) cycloadditions using 1, 4-enynes as five-carbon building blocks. Acc. Chem. Res., 2020, 53: 231–243. doi: 10.1021/acs.accounts.9b00477
    [9]
    Miyaura N, Suzuki A. Palladium-catalyzed cross-coupling reactions of organoboron compounds. Chem. Rev., 1995, 95: 2457–2483. doi: 10.1021/cr00039a007
    [10]
    Suzuki A. Recent advances in the cross-coupling reactions of organoboron derivatives with organic electrophiles, 1995–1998. J. Organomet. Chem., 1999, 576: 147–168. doi: 10.1016/S0022-328X(98)01055-9
    [11]
    Kotha S, Lahiri K, Kashinath D. Recent applications of the Suzuki–Miyaura cross-coupling reaction in organic synthesis. Tetrahedron, 2002, 58: 9633–9695. doi: 10.1016/S0040-4020(02)01188-2
    [12]
    Molander G A, Ellis N. Organotrifluoroborates: Protected Boronic acids that expand the versatility of the Suzuki coupling reaction. Acc. Chem. Res., 2007, 40: 275–286. doi: 10.1021/ar050199q
    [13]
    Tobisu M, Chatani N. Borreagentien für die orthogonale Funktionalisierung mithilfe von Suzuki-Miyaura-Kreuzkupplungen. Angew. Chem. Int. Ed., 2009, 121: 3617–3620. doi: 10.1002/ange.200900465
    [14]
    Lennox A J J, Lloyd-Jones G C. Selection of boron reagents for Suzuki–Miyaura coupling. Chem. Soc. Rev., 2014, 43: 412–443. doi: 10.1039/C3CS60197H
    [15]
    Zhang L, Lovinger G J, Edelstein E K, et al. Catalytic conjunctive cross-coupling enabled by metal-induced metallate rearrangement. Science, 2016, 351: 70–74. doi: 10.1126/science.aad6080
    [16]
    Tucker C E, Davidson J, Knochel P. Mild and stereoselective hydroborations of functionalized alkynes and alkenes using pinacolborane. J. Org. Chem., 1992, 57: 3482–3485. doi: 10.1021/jo00038a044
    [17]
    Miyaura N. Metal-catalyzed reactions of organoboronic acids and esters. Bull. Chem. Soc. Jpn., 2008, 81: 1535–1553. doi: 10.1246/bcsj.81.1535
    [18]
    Zhao M, Shan C C, Wang Z L, et al. Ligand-dependent-controlled copper-catalyzed regio- and stereoselective silaboration of alkynes. Org. Lett., 2019, 21: 6016–6020. doi: 10.1021/acs.orglett.9b02160
    [19]
    Bose S K, Mao L, Kuehn L, et al. First-row d block element-catalyzed carbon–boron bond formation and related processes. Chem. Rev., 2021, 121: 13238–13341. doi: 10.1021/acs.chemrev.1c00255
    [20]
    Alam S, Karim R, Khan A, et al. Copper-catalyzed preparation of alkenylboronates and arylboronates. Eur. J. Org. Chem., 2021, 2021: 6115–6160. doi: 10.1002/ejoc.202100817
    [21]
    Beletskaya I, Pelter A. Hydroborations catalysed by transition metal complexes. Tetrahedron, 1997, 53: 4957–5026. doi: 10.1016/S0040-4020(97)00001-X
    [22]
    Wang Y D, Kimball G, Prashad A S, et al. Zr-mediated hydroboration: stereoselective synthesis of vinyl boronic esters. Tetrahedron Lett., 2005, 46: 8777–8780. doi: 10.1016/j.tetlet.2005.10.031
    [23]
    Iwadate N, Suginome M. Synthesis of B-protected β-styrylboronic acids via iridium-catalyzed hydroboration of alkynes with 1, 8-naphthalenediaminatoborane leading to iterative synthesis of oligo(phenylenevinylene)s. Org. Lett., 2009, 11: 1899–1902. doi: 10.1021/ol9003096
    [24]
    Semba K, Fujihara T, Terao J, et al. Copper-catalyzed borylative transformations of non-polar carbon-carbon unsaturated compounds employing borylcopper as an active catalyst species. Tetrahedron, 2015, 71: 2183–2197. doi: 10.1016/j.tet.2015.02.027
    [25]
    Neeve E C, Geier S J, Mkhalid I A I, et al. Diboron(4) compounds: From structural curiosity to synthetic workhorse. Chem. Rev., 2016, 116: 9091–9161. doi: 10.1021/acs.chemrev.6b00193
    [26]
    Ojha D P, Prabhu K R. Pd-catalyzed hydroborylation of alkynes: A ligand controlled regioselectivity switch for the synthesis of α- or β-vinylboronates. Org. Lett., 2016, 18: 432–435. doi: 10.1021/acs.orglett.5b03416
    [27]
    Yoshida H. Borylation of alkynes under base/coinage metal catalysis: Some recent developments. ACS Catal., 2016, 6: 1799–1811. doi: 10.1021/acscatal.5b02973
    [28]
    Gunanathan C, Hölscher M, Pan F, et al. Ruthenium catalyzed hydroboration of terminal alkynes to Z-vinylboronates. J. Am. Chem. Soc., 2012, 134: 14349–14352. doi: 10.1021/ja307233p
    [29]
    Yamamoto K, Mohara Y, Mutoh Y, et al. Ruthenium-catalyzed (Z)-selective hydroboration of terminal alkynes with naphthalene-1, 8-diaminatoborane. J. Am. Chem. Soc., 2019, 141: 17042–17047. doi: 10.1021/jacs.9b06910
    [30]
    Obligacion J V, Neely J M, Yazdani A N, et al. Cobalt catalyzed Z-selective hydroboration of terminal alkynes and elucidation of the origin of selectivity. J. Am. Chem. Soc., 2015, 137: 5855–5858. doi: 10.1021/jacs.5b00936
    [31]
    Ben-Daat H, Rock C L, Flores M, et al. Hydroboration of alkynes and nitriles using an α-diimine cobalt hydride catalyst. Chem. Commun., 2017, 53: 7333–7336. doi: 10.1039/C7CC02281F
    [32]
    Zhang G, Li S, Wu J, et al. Highly efficient and selective hydroboration of terminal and internal alkynes catalysed by a cobalt (II) coordination polymer. Org. Chem. Front., 2019, 6: 3228–3233. doi: 10.1039/C9QO00834A
    [33]
    Chen J, Shen X, Lu Z. Cobalt-catalyzed Markovnikov-type selective hydroboration of terminal alkynes. Angew. Chem. Int. Ed., 2021, 60: 690–694. doi: 10.1002/anie.202012164
    [34]
    Pereira S, Srebnik M. A study of hydroboration of alkenes and alkynes with pinacolborane catalyzed by transition metals. Tetrahedron Lett., 1996, 37: 3283–3286. doi: 10.1016/0040-4039(96)00576-X
    [35]
    Ohmura T, Yamamoto Y, Miyaura N. Rhodium- or Iridium-catalyzed trans-hydroboration of terminal alkynes, giving (Z)-1-alkenylboron compounds. J. Am. Chem. Soc., 2000, 122: 4990–4991. doi: 10.1021/ja0002823
    [36]
    Lee T, Baik C, Jung I, et al. Stereoselective hydroboration of diynes and triyne to give products containing multiple vinylene bridges:   A versatile application to fluorescent dyes and light-emitting copolymers. Organometallics, 2004, 23: 4569–4575. doi: 10.1021/om049832m
    [37]
    Lyu Y, Toriumi N, Iwasawa N. (Z)-Selective hydroboration of terminal alkynes catalyzed by a PSP–pincer rhodium complex. Org. Lett., 2021, 23: 9262–9266. doi: 10.1021/acs.orglett.1c03606
    [38]
    Takahashi K, Ishiyama T, Miyaura N. A borylcopper species generated from bis(pinacolato)diboron and its additions to α, β-unsaturated carbonyl compounds and terminal alkynes. J. Organomet. Chem., 2001, 625: 47–53. doi: 10.1016/S0022-328X(00)00826-3
    [39]
    Jang H, Zhugralin A R, Lee Y, et al. Highly selective methods for synthesis of internal (α-) vinylboronates through efficient NHC–Cu-catalyzed hydroboration of terminal alkynes. Utility in chemical synthesis and mechanistic basis for selectivity. J. Am. Chem. Soc., 2011, 133: 7859–7871. doi: 10.1021/ja2007643
    [40]
    Moure A L, Mauleón P, Arrayás R G, et al. Formal regiocontrolled hydroboration of unbiased internal alkynes via borylation/allylic alkylation of terminal alkynes. Org. Lett., 2013, 15: 2054–2057. doi: 10.1021/ol4007663
    [41]
    Yoshida H, Takemoto Y, Takaki K. A masked diboron in Cu-catalysed borylation reaction: highly regioselective formal hydroboration of alkynes for synthesis of branched alkenylborons. Chem. Commun., 2014, 50: 8299–8302. doi: 10.1039/C4CC01757A
    [42]
    Zhang P, Suárez J M, Driant T, et al. Cyclodextrin cavity-induced mechanistic switch in copper-catalyzed hydroboration. Angew. Chem. Int. Ed., 2017, 56: 10821–10825. doi: 10.1002/anie.201705303
    [43]
    Gao Y, Yazdani S, Kendrick IV A, et al. Cyclic (alkyl)(amino)carbene ligands enable Cu-catalyzed Markovnikov protoboration and protosilylation of terminal alkynes: A versatile portal to functionalized alkenes. Angew. Chem. Int. Ed., 2021, 60: 19871–19878. doi: 10.1002/anie.202106107
    [44]
    Tsushima T, Tanaka H, Nakanishi K, et al. Origins of internal regioselectivity in copper-catalyzed borylation of terminal alkynes. ACS Catal., 2021, 11: 14381–14387. doi: 10.1021/acscatal.1c04244
    [45]
    Chen J, Gao S, Gorden J D, et al. Stereoselective syntheses of γ-boryl substituted syn-β-alkoxy- and syn-β-amino-homoallylic alcohols via a regio- and stereoselective allene diboration and aldehyde allylboration reaction sequence. Org. Lett., 2019, 21: 4638–4641. doi: 10.1021/acs.orglett.9b01535
    [46]
    Caspers L D, Finkbeiner P, Nachtsheim B J. Direct electrophilic C−H alkynylation of unprotected 2-vinylanilines. Chem. Eur. J., 2017, 23: 2748–2752. doi: 10.1002/chem.201606026
    [47]
    Sato T, Onuma T, Nakamura I, et al. Platinum-catalyzed cycloisomerization of 1, 4-enynes via 1, 2-alkenyl rearrangement. Org. Lett., 2011, 13: 4992–4995. doi: 10.1021/ol202104c

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