Ring expansion-annulation strategy for the synthesis of substituted azulenes and oligoazulenes. 2. Synthesis of azulenyl halides, sulfonates, and azulenylmetal …

…, JL Kane, KM Shea, RL Danheiser

Index: Crombie, Aimee L.; Kane Jr., John L.; Shea, Kevin M.; Danheiser, Rick L. Journal of Organic Chemistry, 2004 , vol. 69, # 25 p. 8652 - 8667

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Citation Number: 57

Abstract

A “ring expansion-annulation strategy” for the synthesis of substituted azulenes is described based on the reaction of β'-bromo-α-diazo ketones with rhodium carboxylates. The key transformation involves an intramolecular Büchner reaction followed by β-elimination of bromide, tautomerization, and in situ trapping of the resulting 1-hydroxyazulene as a carboxylate or triflate ester. Further synthetic elaboration of the azulenyl halide and ...