Facile coupling of propargylic, allylic and benzylic alcohols with allylsilane and alkynylsilane, and their deoxygenation with Et 3SiH, catalyzed by Bi(OTf) 3 in [BMIM][BF 4] ionic liquid (IL), with recycling and reuse of the IL
Allyltrimethylsilane (allyl-TMS) reacts with propargylic alcohols 1a-1d in the presence of 10% Bi(OTf) 3 in [BMIM][BF 4] solvent to furnish the corresponding 1,5-enynes in respectable isolated yields (87-93%) at room temperature. The utility of Bi(OTf) 3 as a superior catalyst was demonstrated in a survey study on coupling of allyl-TMS with 1a employing several metallic triflates (Bi, Ln, Al, Yb) as well as, B(C 6F 5) 3, Zn(NTf 2) 2 and Bi(NO 3) 3·5H 2O. Coupling of cyclopropyl substituted propargylic alcohol 1e with allyl-TMS gave the skeletally intact 1,5-enyne and a ring opened derivative as a mixture. Coupling of propargylic/allylic alcohol 1f with allyl-TMS resulted in allylation at both benzylic (2 isomers) and propargylic positions, as major and minor products respectively. The scope of this methodology for allylation of a series of allylic and benzylic alcohols was explored. Chemoselective reduction of a host of propargylic, propagylic/allylic, bis-allylic, allylic, and benzylic alcohols with Et 3SiH was achieved in high yields with short reaction times. The same approach was successfully applied to couple representative propargylic and allylic alcohols with 1-phenyl-2-trimethylsilylacetylene. The recovery and reuse of the ionic liquid (IL) was gauged in a case study with minimal decrease in isolated yields after six cycles. © 2012 The Royal Society of Chemistry.
Organic and Biomolecular Chemistry
Digital Object Identifier (DOI)
Kumar, G & Laali, Kenneth. (2012). Facile Coupling of Propargylic, Allylic and Benzylic Alcohols with Allylsilane and Alkynylsilane, and Their Deoxygenation with Et3SiH, Catalyzed by Bi(OTf)3 in [BMIM][BF4] Ionic Liquid (IL), with Recycling and Reuse of the IL. Organic & biomolecular chemistry. 10. 7347-55. 10.1039/c2ob26046h.