Comparison of Approaches to ent-Morphine via Radical, Cationic, and Heck-Type Cyclizations
3-(2-{6S-(2-Bromo-6-methoxyphenoxy)-5S-[tert-butyl(dimethyl)silyloxy)cyclohex-1-en-1-yl}ethyl)oxazol-2(3H)-one 14 was subjected to Heck cyclization conditions to afford diben- zofuran derivative 16. The comparison of stepwise vs cascade approaches to 8 via radical, cationic, and Heck-type cyclizations is discussed.