INTRAMOLECULAR VINYL RADICAL CYCLIZATION REACTIONS OF CYCLOHEXADIENESDERIVED FROM SEQUENTIAL ADDITIONS TO (ARENE)(TRICARBONYL)CHROMIUM COMPLEXES

Cyclohexa-1,3-dienes 7-10 with a 1,5,6-substitution pattern were prepa red in a one-pot reaction sequence by sequential addition of MeLi and propargyl bromides to the tricarbonylchromium complex la. These produc ts were subjected to radical cyclization procedures. Vinyl radical gen eration by Bu(3)Sn addition to the propargyl group in 7-10 was followe d by regio- and diastereoselective intramolecular ring closure. Two di fferent 5-exo-trig cyclizations are possible via different vinyl radic al intermediates and cyclization to one or the other of the termini of the cyclohexadiene moiety. Internal alkynes reacted to yield exclusiv ely the cis-fused hexahydroindene products 12-14 whereas the terminal alkyne yielded bicyclo[3.2.l]octenes 11 as sole products.