Highly Stereospecific Cyclizations of Homoallylic Silanols
Anand H Shinde1, Ranjeet A Dhokale1, Joel T Mague2
1Department of Medicinal Chemistry, University of Kansas, Lawrence, Kansas 66047, United States.
Abstract:
We demonstrate that di-tert-butylsilanols are competent nucleophiles for the intramolecular interception of palladium π-allyl species. In these reactions, allyl ethyl carbonates are the best precursors for the formation of palladium π-allyl intermediates, and [(Cinnamyl)PdCl]2/BINAP is superior to other Pd salt/ligand framework combinations. Our optimized protocol is compatible with a variety of silanol substrates. Importantly, the cyclization is perfectly stereospecific, proceeding via an anti-syn mechanism, which stands in contrast to reported analogous reactions of alcohols and phenols, known to proceed via an anti-anti mechanism. The alkenes in the product dioxasilinanes serve as blank slates for further functionalization.
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