REACTIONS OF DIALKOXYCARBENES WITH TETHERED TRIPLE BONDS TO FORM HETEROCYCLIC-COMPOUNDS

Dialkoxycarbenes with a tethered triple bond, generated from the corre sponding oxadiazolines, under go an intramolecular cyclization with th e tethered alkyne moiety to give 3,3-dialkoxyvinylcarbene/ 1,3-dipole intermediates. The regioselectivity of the carbene cyclization is high ly dependent upon the nature of the alkyne substituent. In the cases w here an exocyclic vinylcarbene is generated, the vinylcarbene intermed iate can undergo a synthetically useful [3+2] cycloaddition with eithe r an appropriate olefin or an alkyne. This approach allows the rapid c onstruction of some interesting heterocyclic ring systems.