Carbocyclization reaction of omega-iodo- and 1,omega-diiodo-1-alkynes without the loss of iodine atoms through a carbenoid-chain process.

Atom-economical carbocyclization reactions of omega-iodo-1-alkynes and 1,omega-diiodo-1-alkynes to give products with incorporation of iodine atoms is described. Cycloisomerization of 2-(2-propynyloxy)ethyl iodides is initiated by a catalytic amount of LDA to give 3-(iodomethylene)tetrahydrofurans in high yields. Upon treatment of with a catalytic amount of 1-hexynyllithium, 1,omega-diiodo-1-alkynes efficiently undergo cycloisomerization to give (diiodomethylene)cycloalkanes.

Novel cyclization reaction of 1,omega-diiodo-1-alkynes without the loss of iodine atoms.

In the presence of 1-hexynyllithium (0.2-0.6 equiv.