An alternative general preparation of 2-alkyl-1-benzostannepines and theirconversion into 1-benzostibepines and 1-benzoborepines via a tin-metal exchange

The 2-alkyl-1-benzostannepines 4a-g were prepared by the intramolecular hyd rostannation of the tin intermediates 3 to an acetylenic moiety in one pot from (Z)-1-(o-bromophenyl)but-1-en-3-ynes 1. The obtained stannepines 4 wer e easily converted into the 1-benzostibepines 9, 10, 11, 12 and the 1-benzo borepines 14, 15 by tin-antimony and tin-boron exchange reactions in modera te to good yields, respectively. The 1-benzoborepines 14 and 15 are hithert o unknown heterocyclic ring systems.