Synlett 2010(15): 2279-2282  
DOI: 10.1055/s-0030-1258028
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

Diastereoselective Construction of New 5a-Substituted Carbaallose by exo-β-Selective Conjugate Addition to endo-exo Cross-Conjugated Cyclohexadienone as Key Reaction

Takashi Fujishima, Fukashi Kitoh, Tomotsugu Yano, Ryo Irie*
Department of Chemistry, Graduate School of Science and Technology, Kumamoto University, 2-39-1 Kurokami, Kumamoto 860-8555, Japan
Fax: +81(96)3423379; e-Mail: irie@sci.kumamoto-u.ac.jp;
Further Information

Publication History

Received 17 June 2010
Publication Date:
09 August 2010 (online)

Abstract

Practical synthesis of a new chiral endo-exo cross-conjugated cyclohexadienone was achieved, and its synthetic utility was illustrated by highly exo-β-selective conjugate addition with various nucleophiles. Further diastereoselective transformation of the adduct to an unprecedented 5a-substituted carbaallose is also described.

8

We have deposited the crystallographic data for 3 with the Cambridge Crystallographic Data Center as supplementary publication number CCDC 779019.

12

This byproduct could be the diastereomer of 6e. However, no confirmation has been yet obtained as these two products are not separated by TLC and their ¹H NMR signals (600 MHz) are extensively overlapping.

14

We have deposited the crystallographic data for 10 with the Cambridge Crystallographic Data Center as supplementary publication number CCDC 779020.

15

In a preliminary experiment, the enantioenriched dienone 5 (90% ee) was obtained by asymmetric Kornblum DeLaMare rearrangement of 3 under Toste’s conditions.¹6 For details, see the Supporting Information.