Synthesis of allylic and homoallylic alcohols from unsaturated cyclic ethers using a mild and selective C–O reduction approach

Abstract

Unsaturated cyclic ethers can be mildly and selectively reduced with catalytic amounts of B(C(6)F(5))(3) in the presence of an alkylsilane. The allylic position is preferentially reduced with minimal or no scrambling of olefin geometry. For electronically equivalent substrates, steric factors guide the reducing agent to the least substituted site.

Catalytic Ketone Hydrodeoxygenation Mediated by Highly Electrophilic Phosphonium Cations

“…It is noteworthy that in closely related chemistry,B(C 6 F 5 ) 3 has been shown to catalyze the deoxygenation of unsaturated cyclic ethers and silyl ethers, [23] thus affording allylic and homoallylic alcohols [26] and siloxanes,r espectively. [27] In addition B(C 6 F 5 ) 3 has also been used to dehydrocouple silanes with alcohols [28] to give silylethers.…”

Catalytic Reduction of Cyclic Ethers with Hydrosilanes

“…Based on the report by Gevorgyan and Yamamoto, Njardarson et al. explored the 8 ‐catalyzed C−O reduction of 2,5‐dihydrofurans and 3,6‐2 H ‐dihydropyrans with Et 3 SiH (1.1 equiv) . The reaction scope was broad, with excellent regioselectivity for ring opening, which was sensitive to the electrostatic nature of ethereal C−O bonds (Scheme ).…”

“…Based on the reportb yG evorgyan and Yamamoto, [43] Njardarson et al explored the 8-catalyzed CÀOr eduction of 2,5-dihydrofurans and 3,6-2 H-dihydropyransw ith Et 3 SiH (1.1 equiv). [44] The reaction scope wasb road, with excellent regioselectivity for ring opening, which was sensitive to the electrostatic nature of etherealC ÀOb onds (Scheme27). Most of dihydro substrates smoothly underwent hydrosilylation with-out olefin isomerization to give silyl-protected allylic and homoallylic alcohols in yields of 75-96 %i nt he presence of 8 (5 mol %).…”

Catalytic Ketone Hydrodeoxygenation Mediated by Highly Electrophilic Phosphonium Cations

“…It is noteworthy that in closely related chemistry, B(C 6 F 5 ) 3 has been shown to catalyze the deoxygenation of unsaturated cyclic ethers and silyl ethers,23 thus affording allylic and homoallylic alcohols26 and siloxanes, respectively 27. In addition B(C 6 F 5 ) 3 has also been used to dehydrocouple silanes with alcohols28 to give silylethers.…”