Reactions of dialkoxycarbenes with tethered triple bonds to form heterocyclic compounds

Dialkoxycarbenes with a tethered triple bond, generated from the corresponding oxadiazolines, under go an intramolecular cyclization with the tethered alkyne moiety to give 3,3-dialkoxyvinylcarbene/ 1,3-dipole intermediates. The regioselectivity of the carbene cyclization is highly dependent upon the nature of the alkyne substituent. In the cases where an exocyclic vinylcarbene is generated, the vinylcarbene intermediate can undergo a synthetically useful [3+2] cycloaddition with either an appropriate olefin or an alkyne. This approach allows the rapid construction of some interesting heterocyclic ring systems.