Rhodium(I)-Catalyzed Decarbonylative Spirocyclization through CC Bond Cleavage of Benzocyclobutenones: An Efficient Approach to Functionalized Spirocycles
作者:Tao Xu、Nikolas A. Savage、Guangbin Dong
DOI:10.1002/anie.201310149
日期:2014.2.10
The rhodium‐catalyzed formation of all‐carbon spirocenters involves a decarbonylative coupling of trisubstituted cyclic olefins and benzocyclobutenones through CC activation. The metal–ligand combination [Rh(CO)2Cl}2]/P(C6F5)3 catalyzed this transformation most efficiently. A range of diverse spirocycles were synthesized in good to excellent yields and many sensitive functional groups were tolerated
Total synthesis of the unnatural enantiomer of deacetylravidomycin M was accomplished. The key steps include, (1) aryl C-glycosidation of the azido-bearing fucosyl acetate 2 by using catalytic Sc(OTf)3, (2) the [2+2] cycloaddition reaction of alkoxybenzyne bearing an azido sugar to ketene silyl acetal, and (3) the ring expansion reaction of alkoxybenzocyclobutenone. The synthesis revealed that the
tetracenomycins C and X were achieved, featuring 1) preparation of a hexasubstituted naphthonitrile oxide by successive benzyne cycloadditions and an oxidative ring‐opening reaction; 2) a novel ortho‐quinone mono‐acetal as the A‐ring unit; 3) construction of three contiguous stereogenic centers by an asymmetric benzoin cyclization, an isoxazole oxidation, and a stereoselective reduction.
An efficient, flexible route to highly functionalized linearly fused dicyclobutabenzenes is described based on the dual, regioselective cycloaddition of benzyne and ketene silyl acetals.