Construction of spirocarbocyclic scaffolds through dearomatization using calcium carbide as an alkyne source
Zhiqiang Wang1, Botao Wang1, Jiao Wang1
1College of Chemistry and Chemical Engineering, Northwest Normal University, Lanzhou, Gansu, 730070, P. R. China. lizheng@nwnu.edu.cn.
Abstract:
A novel method for the one-step construction of spirocarbocyclic scaffolds by dearomatizing annulation is described. A number of spiro[indene-1,1'-naphthalen]-2'-ones are efficiently synthesized by reactions of 1-arylnaphthalen-2-ols with aryl iodides and calcium carbide through Csp2-H activation and simultaneous formation of four C-C bonds. Meanwhile, a series of spiro[cyclopentane-1,1'-naphthalene]-2,4-dien-2'-ones are effectively obtained by reactions of 1-bromonaphthalen-2-ols with aryl iodides and calcium carbide through cross-coupling and simultaneous formation of seven C-C bonds. The salient feature of this protocol is the use of an inexpensive and easy-to-handle solid alkyne source as a substitute for flammable and explosive gaseous acetylene. In addition, satisfactory yields and a simple workup procedure are also advantages of this method. The corresponding products can also be synthesized on a gram scale.
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