Highly Chemoselective Calcium‐Catalyzed Propargylic Deoxygenation

Abstract

A calcium-catalyzed direct reduction of propargylic alcohols and ethers has been accomplished by using triethylsilane as a nucleophilic hydride source. At room temperature a variety of secondary propargylic alcohols was deoxygenated to the corresponding hydrocarbons in excellent yields. Furthermore, for the first time, a catalytic deoxygenation of tertiary propargylic alcohols was generally applicable. The same protocol was suitable for an efficient reduction of secondary as well as tertiary propargylic methyl, benzyl and allyl ethers. Substrates containing an additional keto-, ester or secondary hydroxyl function were reduced with exceptional chemoselectivity at the propargylic position.

Recent Advances in Transition-Metal Catalyzed Defunctionalization Reaction

“…图式 32 锰催化酰胺脱氧反应 Scheme 32 Manganese catalyzed deoxygenation of amide 汞催化 [97] 的脱羧反应、钛催化 [98] 的脱羟基化反应、 钙介导 [99] 的炔醇脱羟基化反应以及以碳酸铯作碱 [100] 的 分子内脱羧反应陆续得以发展.…”

Calcium-catalyzed reactions of element-H bonds

“…For example, with the catalytic Ca(NTf 2 ) 2 /Bu 4 NPF 6 system, the propargyl alcohol (ether) 46 was reduced by Et 3 Si-H to alkene 47 in up to 98% yield (Eq. ( 14)) [64]. The reaction proceeded quickly at room temperature and finished within 5-10 min.…”

Reductive Deoxygenation of Alcohols: Catalytic Methods Beyond Barton–McCombie Deoxygenation

“…[62] The mechanism involves the initial formation of the silyl ether followed by deoxygenation by hydride transfer. The Ca(NTf 2 ) 2 -catalyzed reaction was enhanced by using Bu 4 NPF 6 as an additive, [64] whereas the deoxygenation catalyzed by Bi(OTf) 2 was performed in the ionic liquid [BMIM][BF 4 ] (BMIM = 1-butyl-3-methylimidazolium). Scheme 25.…”