Active metals Acyl bromides

Previous syntheses An example of this point can be recognized by examination of one known synthesis of thienobenzazepines (Scheme 6.1). This synthetic route involves a key palladinm-catalyzed cross-conpling of stannyl intermediate 3, prepared by method of Gronowitz et al., with 2-nitrobenzyl bromide. Acetal deprotection and reductive cyclization afforded the desired thienobenzazepine tricycle 4. In support of structure activity relationship studies, this intermediate was conveniently acylated with varions acyl chlorides to yield several biologically active componnds of structure type 5. While this synthetic approach does access intermediate 4 in relatively few synthetic transformations for stractnre activity relationship studies, this route is seemingly nnattractive for preparative scale requiring stoichiometric amounts of potentially toxic metals that are generally difficult to remove and present costly purification problems at the end of the synthesis. 

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