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Synlett 2011(11): 1579-1584  
DOI: 10.1055/s-0030-1260775
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

Dramatic Base-Oriented Chemoselective Tandem Wacker Cyclizations: Synthesis of Bisbenzannelated Spiroketals and 2-Substituted Chromans

Zhijun Xin, Yuan Zhang, Hua Tao, Jijun Xue*, Ying Li*
State Key Laboratory of Applied Organic Chemistry, Lanzhou University, Lanzhou 730000, P. R. of China
Fax: +86(931)8912582; e-Mail: xuejj@lzu.edu.cn; e-Mail: liying@lzu.edu.cn;
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Publication History

Received 7 March 2011
Publication Date:
10 June 2011 (online)

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Abstract

A Pd(II)/Cu(II)-catalyzed chemoselective tandem aerobic cyclization of phenolic olefins leads to [5,6]-bisbenzannelated spiroketals or 2-substituted chromans, wherein it was interestingly found that the presence or absence of base could be responsible for the tunable selectivity. The [5,6]-bisbenzannelated spiroketals were achieved from tandem Wacker cyclization-aroxylation in moderate yields in the absence of base, and 2-substituted chromans were formed through base-mediated Pd(II)/Cu(II)-catalyzed tandem Wacker cyclization-Michael addition in good yields.

Key words

palladium - chemoselectivity - spiroketals - chromans - Wacker cyclization