New mixed metal (Mn/Cu) catalyzed stereoselective cyclizations
摘要:
Unsaturated alkyl bromides of type 1 undergo a stereoselective ring closure when treated with a MnBr2 (5 mol%)/CuCl (3 mol%) catalytic mixed metal system and diethylzinc at 60 degrees C in DMPU affording five membered carbo- and heterocycles. An alternative Ni-catalyzed cyclization of bromoalkylketones is also described. Remarkably in this case, the iodine-zinc exchange could be performed with EtZnBr instead of pyrophoric Et(2)Zn. Copyright (C) 1996 Elsevier Science Ltd
Rearrangements of Bicyclic Nitrones to Lactams: Comparison of Photochemical and Modified Barton Conditions
作者:Yibin Zeng、Brenton T. Smith、John Hershberger、Jeffrey Aubé
DOI:10.1021/jo035004b
日期:2003.10.1
The rearrangement of nitrones to lactams can be carried out by photochemical activation or by treatment with Tf(2)O followed by KOH-promoted rearrangement (a modification of conditions originally introduced by Barton). Substrates in which the nitrone is part of a fused bicyclic ring system have traditionally proven problematic for this kind of reaction. In this study, a series of mono-, bi-, and tricyclic