Duplicated ring enlargement of 4,9-methanothia[11]annulene to 6,11-methanothia[15]annulene
摘要:
3,10-Dipyrrolidinyl-4,9-methanothia[11]annulene reacts with excess dimethyl acetylenedicarboxylate (DMAD) in refluxing toluene to give ring-enlarged 6,11-methanothia[15]annulene. X-ray crystallographic analysis of the product shows two different cis,trans-dienyl parts in the ring system. Product formation possibly involves pi-facial selective addition of the enamine with DMAD and torque-selective ring opening of the intermediate cyclobutenes. (c) 2010 Elsevier Ltd. All rights reserved.