Synthesis 2006(8): 1351-1359  
DOI: 10.1055/s-2006-926399
PAPER
© Georg Thieme Verlag Stuttgart · New York

Additions of Lithiated Alkoxyallenes to Phthalimide: A New Synthesis of Pyrroloisoindolones and an Unusual Olefination Reaction

Silvia Kaden, Hans-Ulrich Reissig*, Irene Brüdgam, Hans Hartl
Freie Universität Berlin, Institut für Chemie und Biochemie, Takustrasse 3, 14195 Berlin, Germany
Fax: +49(30)83855367; e-Mail: hans.reissig@chemie.fu-berlin.de;
Further Information

Publication History

Received 6 October 2005
Publication Date:
27 March 2006 (online)

Abstract

Addition of an excess of lithiated alkoxyallenes to phthalimide­ 5 provided the expected primary adducts 7a-c, which could be cyclized via their oxygen moiety to furnish spirofuran derivatives 8a-c. After selective protection of the hydroxyl function of 7a-c the resulting siloxy derivatives 11a-c were transformed by gold(III) catalysis into pyrroloisoindolones 13a-c in moderate yields. This establishes a new approach to this class of heterocycles in a [3+2] fashion with the alkoxyallenes as functionalized C-3 unit and phthalimide 5 providing the CN moiety. Treatment of primary adducts 7a-c with aqueous sulfuric acid surprisingly led to compounds 14a-c in good yields. The constitution of these products was proved by an X-ray analysis of derivative 15a. Aqueous hydrochloric acid converted 7a into a similar product 17 containing a chlorine substituent. These reactions can be considered as olefination reactions of phthalimide.

19

Crystallographic data for 15a can be obtained from Cambridge Crystallographic Data Centre, CCDC reference number: 286363.