Magnesium mediated carbometallation of propargyl alcohols: direct routes to furans and furanones

The addition of vinyl and aryl Grignard reagents to propargyl alcohols for the direct synthesis of furans and butenolides from a one pot reaction is described. These products arise from a putative magnesium chelate intermediate 2 upon reaction with various electrophiles. This chelate was also generated in situ from alkynyl lithium addition to aldehydes followed by magnesium exchange and Grignard addition. Thus, the complete substitution pattern for the furan ring may be controlled, as desired, through the judicious choice of substrates and reagents.