Ligand Assisted Rhodium Catalyzed Selective Semi‐hydrogenation of Alkynes Using Syngas and Molecular Hydrogen,ChemistrySelect

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Ligand Assisted Rhodium Catalyzed Selective Semi‐hydrogenation of Alkynes Using Syngas and Molecular Hydrogen
ChemistrySelect ( IF 1.9 ) Pub Date : 2018-01-15 , DOI: 10.1002/slct.201702976
Samadhan A. Jagtap ₁ , Bhalchandra M. Bhanage ₁

Affiliation

This work reports the Rhodium catalyzed selective semi‐hydrogenation of alkynes to (E) and (Z)‐alkenes in the presence of various Buchwald phosphine ligands such as S‐Phos (L₁), t‐Bu XPhos (L₂), Ru‐Phos (L₃), Johnphos (L₄) and DavePhos (L₅). Selective formation of E‐alkenes in high activity with use of H₂ gas (5 bar) is an alternative method for conventional Birch reduction. High selectivity obtained towards Z‐alkenes with use of syngas (10 bar) is an alternative method for Lindlar reaction. (E)‐alkenes were obtained in high yield due to the steric crowding present in L₄ ligand. The carbon monoxide present in syngas controls over‐hydrogenation of alkynes and (Z)‐alkenes were obtained as major product due to cis addition of molecular hydrogen to alkynes. The use of additives, base, co‐catalyst and excess use of chemicals is prevented with this protocol for semi‐hydrogenation reaction. With this simple and effective catalyst system and mild reaction conditions, internal as well as terminal alkynes were smoothly converted to respective alkenes in high yield (>90%).

中文翻译：

合成气和分子氢的配体辅助铑催化的炔烃选择性半加氢反应

这项工作报告了在各种Buchwald膦配体如S-Phos（L ₁），t- Bu XPhos（L ₂），Ru的存在下，铑催化的炔烃选择性半氢化为（E）和（Z）-烯烃。-Phos（L ₃），Johnphos（L ₄）和DavePhos（L ₅）。使用H ₂气（5巴）以高活性选择性形成E-烯烃是常规桦木还原的另一种方法。对Z的选择性高使用合成气（10 bar）的烯烃是Lindlar反应的另一种方法。由于L ₄配体中存在空间拥挤，以高收率获得了（E）-烯烃。合成气中存在的一氧化碳可控制炔烃的加氢，由于向炔烃中顺式添加了分子氢，因此获得了（Z）烯烃作为主要产物。通过此协议，可以防止半氢化反应使用添加剂，碱，助催化剂和化学品的过量使用。通过这种简单有效的催化剂体系和温和的反应条件，内部和末端炔烃均可以高收率（> 90％）平稳地转化为相应的烯烃。

更新日期：2018-01-15

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