Indium-mediated Prins cyclization using allyllic silicon as allylating reagent

ORGN 167

Kok Ping Chan and Teck Peng Loh. Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore, Singapore
Tetrahydropyran rings are part of important backbones of many complex natural products. Prins cyclization is a fundamental acid-catalysed olefin-aldehyde condensation for the formation of the pyran ring. A one-pot-three-components Prins cyclization was developed with high yield and selectivity. The three components system comprises of allylchlorosilane or allylsilanol, Lewis acid (Indium based) and aldehydes. The 2,4,6-substituted tetrapyran product formed from the one-pot reaction exhibits high specificity, depending on (i) the type and amount of allylating agent used; (ii) the type of Lewis acid used; (iii) the sequence of aldehyde added.