A comparative study of the decomposition of o-alkynyl-substituted aryl diazo ketones. Synthesis of polysubstituted .beta.-naphthols via arylketene intermediates
摘要:
The photochemical, thermal, and rhodium-catalyzed decomposition reactions of several closely related o-alkynyl or o-alkenyl alpha-diazoaceto- and propiophenone derivatives have been studied. The reaction outcome is markedly dependent upon the reaction conditions employed for nitrogen extrusion. Thermolysis or photolysis of o-alkynyl alpha-diazopropiophenone derivatives yields polysubstituted beta-naphthols. These products are derived from Wolff rearrangement of the initially formed carbene to give an aryl ketene which undergoes intramolecular cyclization onto the o-alkynyl substituent. In direct contrast to the thermal and photochemical results, Rh(II)-catalyzed decomposition yields products derived from direct attack of a rhodium carbenoid onto the tethered pi-system producing a vinyl carbenoid intermediate. Further reaction of the cyclized carbenoid with the starting diazo compound furnishes a vinyl indenone which undergoes a rapid intramolecular Diels-Alder reaction to produce a novel dimer whose structure was elucidated by an X-ray crystal analysis. Replacement of the methyl group on the diazo center with a sterically less demanding hydrogen atom was also found to play an important role in controlling the outcome of the Rh(II)-catalyzed reaction.
Rearrangement of o-alkynyl substituted α-diazoacetophenones. Conversion to β-naphthols via arylketene intermediates
作者:Albert Padwa、David J. Austin、Ugo Chiacchio、Jamal M. Kassir、Antonio Rescifina、Simon L. Xu
DOI:10.1016/s0040-4039(00)79427-5
日期:1991.10
In contrast to the rhodium (II) mediated cycloisomerization of o-alkynyl substituted α-diazoacetophenones, irradiation leads to β-naphthols which are formed via cyclization of an arylketene intermediate.