Palladiumcatalysed tandem cyclisation-anion capture processes initiated by oxidative addition of benzylic or allylic halides or acetates to Pd(O) occure regio- and stereo- specifically in good yield. Examples of “anion” capture involving formate (H−), and organo - tin, -zinc, and -boron species are described.
Atom Transfer Cyclization Catalyzed by InCl<sub>3</sub> via Halogen Activation
作者:Gregory R. Cook、Ryuji Hayashi
DOI:10.1021/ol052802a
日期:2006.3.1
[reaction: see text] Indium trichloride was found to be an efficient catalyst for the cyclization of allylic halides and alkynes with atom transfer in methylene chloride. Mechanistic evidence supports a cationic reaction pathway with Lewis acid activation of the allylic halogen. Concomitant nucleophilic attack by the alkyne and trapping with halide led to atom transfer cyclization products. Depending
[Graphics]The cyclization of 1-bromo-2,7- and 1-bromo-2,8-enynes mediated by indium in DMF produced five- and six-membered cyclic compounds. Although KI was a necessary additive in the cyclization of terminal 1-bromo-2,7-enynes to give the desired products at 25degreesC, reactions of terminal 1-bromo-2,8-enynes and internal 1-bromo-2,7-enynes with indium proceeded at 100degreesC in DMF without KI. After cyclizations, subsequent cross-coupling reaction and iodolysis increase the usefulness of this reaction.