Synthesis of biphenanthrenyls and role of C-H•••X noncovalent interactions in conformational control

A convenient synthesis of the 1,2'-biphenanthrenyls 4a-c,f, 1,3'-biphenanthrenyls 4d,e, thiabiphenanthrenyl 4g, the benzo[h]chromen-2-ylideneacetonitrile 5a and the methyl benzo[h]chromen-2-ylideneacetate 5b through carbanion-induced ring transformation of 2H-pyran-2-ones 1 or 2 and the 1-naphthalenone 3a or thiochroman-4-one 3b separately is described. The structures of the biphenanthrenyls 4b and 4c have been confirmed by single-crystal X-ray diffraction. The conformations of 2b, 4b, 4c and 6 have also been studied to establish the role of C-H... X interaction in conformational control. (C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.