We
report a catalytic method for the direct deoxygenation of various
C–O bond-containing functional groups. Using a Ni(II) pre-catalyst
and silane reducing agent, alcohols, epoxides, and ethers are reduced
to the corresponding alkane. Unsaturated species including aldehydes
and ketones are also deoxygenated via initial formation of an intermediate
silylated alcohol. The reaction is chemoselective for C(sp3)–O bonds, leaving amines, anilines, aryl ethers, alkenes,
and nitrogen-containing heterocycles untouched. Applications toward
catalytic deuteration, benzyl ether deprotection, and the valorization
of biomass-derived feedstocks demonstrate some of the practical aspects
of this methodology.
Primary acyl-phosphines are scarce in the literature. Here we show that the reaction of Ph 3 GePCO with the ylide Ph 3 PCH 2 proceeds to give the species Ph 3 PCHC(O)PH-(GePh 3 ) 1. Deprotonation of 1 with Na[N(SiMe 3 ) 2 ] generates the salt [Na(THF) 2 ][Ph 3 PCHC(O)P(GePh 3 )] 2 which provides subsequent access to the bis-germanylated acylphosphine, Ph 3 PCHC(O)P(GePh 3 ) 2 3. Alternatively, treatment of 1 with HCl in dioxane affords the primary acylphosphine Ph 3 PCHC(O)PH 2 4. Compound 4 is a rare example of an air stable primary acyl-phosphines and the first devoid of a stabilizing heteroatom adjacent to the carbonyl fragment. Scheme 1. Selected reactivity of (a) phosphaketenes of the form RPCO (R = SnR 3 , P(NR 2 ) 2 (b) R = GePh 3 c) present work.
The coupling of tertiary alcohols with boronic esters is described, providing a direct access to quaternary carbon scaffolds without needing to proceed by a highly activated intermediate such as an alkyl halide. A dual catalyst system is employed with both Ni(0) and Bi(III) components playing a critical role along with a mild chlorosilane reactant that enhances the yield by alcohol silylation. This method was found to tolerate diverse functional groups including chloro, nitro, olefin, ketone, ester and phenol moieties, while also being applicable to the derivatization of heterocyclic scaffolds. Mechanistic studies suggest the combination of Lewis acid catalyst and organosilane promote heterolytic cleavage of the substrate C-O bond by an SN1-like reaction pathway, providing a powerful strategy for derivatizing readily available alcohols.
A reductive detrifluoromethylation protocol has been developed making use of an earth-abundant alkoxide base and silicon hydride species. A variety of pyridine and quinoline substrates bearing alkyl, aryl, and amino functional groups are reduced in moderate to high yields. The reaction is chemoselective for C(sp 2 )−CF 3 groups located at the 2-position on the pyridine ring, leaving trifluoromethyl groups located elsewhere on the molecule intact. Preliminary mechanistic studies demonstrate that the combination of silane and base generates a strongly reducing system that may transfer an electron to electron-deficient π systems.
Primary acyl‐phosphines are scarce in the literature. Here we show that the reaction of Ph3GePCO with the ylide Ph3PCH2 proceeds to give the species Ph3PCHC(O)PH(GePh3) 1. Deprotonation of 1 with Na[N(SiMe3)2] generates the salt [Na(THF)2][Ph3PCHC(O)P(GePh3)] 2 which provides subsequent access to the bis‐germanylated acylphosphine, Ph3PCHC(O)P(GePh3)2 3. Alternatively, treatment of 1 with HCl in dioxane affords the primary acylphosphine Ph3PCHC(O)PH2 4. Compound 4 is a rare example of an air stable primary acyl‐phosphines and the first devoid of a stabilizing heteroatom adjacent to the carbonyl fragment.
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