Synthetic and spectral studies of novel spiro {bicyclo[3,3,0]actene-8,3 '(2 ' H)-indol}-2 '-ones obtained from indol-2,3-diones

The present article reports our approach toward the synthesis of spiro comp ounds via indol-2,3-diones. Thus, reaction of indol-2,3-dione derivatives w ith a secondary cyclic amino acid namely (R)-(-)-thiazolidine-4-carboxylic acid, affords a thiazolo-oxazolidinone as the main product. When the reacti on is carried out in the presence of a dipolarophile, 1,3-dipolar cycloaddi tion to the intermediate azomethine ylide leads to a novel spiro compound. The products have been characterized on the basis of spectral studies, and the geometry of the intermediate iminium compound has been optimized by use of the semiempirical molecular orbital method. (C) 1999 John Wiley & Sons, Inc.