Synthetic studies of the tandem enediyne-mono- and bisradical cyclizations

The readily synthesis enediynes 12a-j posssessing a tethered olefin radical acceptor can participate in a tandem enediyne-radical cyclization to yield dihydrobenzindene derivatives 14a-j. In the present study, the scope of thin reaction was expanded to include a wide variety of olefin acceptors. Substitution at both ends of olefin leads to the formation of two diastereomers 14b and 14c in a 3.5:1 ratio when R 3 is Me and R 2 is CO 2 Me. The structures of the dihydrobenzindene products 14b and 14c were confirmed by generating a radical from 25 by a tributyltin hydride reaction which undergoes radical cyclization; thin radical in similar to the enediyne-generated radical, which also cyclizes