June 2024

We have developed an efficient method for the synthesis of 2,3-dihydro-1H-1-benzosiloles in 19% to 90% isolated yield from 1-hydrosilyl-2-ethynylbenzenes by using two equivalents of diisobutylaluminum hydride. The reaction mechanism involves regioselective double hydroalumination of the alkyne moiety followed by cyclization to a 2-alanyldihydrobenzosilole. A silacyclopentane (silolane) was also synthesized in 97% isolated yield from the corresponding 4-silylbut-1-yne under the same reaction conditions. Although the substrate-scope study was conducted on a 0.5-mmol scale, a gram-scale reaction of (2-ethynylphenyl)(diphenyl)silane under the optimized reaction conditions successfully afforded the desired product in 94% isolated yield without loss of reactivity.

The NBS-mediated organocatalytic cascade synthesis of 4,5-dihydronaphtho[2,1-b]furan-1-carbaldehydes from α,β-unsaturated aldehydes and 2-tetralones have been developed. In this synthesis strategy, the C1 of in situ generated brominated 2-tetralone was used as identical twin electron donor–acceptor, and the Cβ and Cα of enals were used as the heterogeneous twin electron acceptor–donors. The process has been realized by a synergistic amine/p-TSA catalyzed one-pot cascade Michael addition–cyclopropanation–ring opening–oxa-Michael addition under mild conditions and without the use of transition metals.