A catalyst system comprising palladium acetate-bidentate phosphine is effective for the cyclocarbonylation of o-iodoanilines with heterocumulenes at 70-100 degrees C for 12-24 h to give the corresponding 4(3H)-quinazolinone derivatives in good yields. Utilizing o-iodoaniline with isocyanates, carbodiimides, and ketenimines for the reaction, 2,4-(1H,3H)-quinazolinediones, 2-amino-4(3H)-quinazolinones and 2-alkyl-4(3H)-quinazolinones were obtained, respectively. The nature of the substrates including the electrophilicity of the carbon center of the carbodiimide, and the stability of the ketenimine, influence the product yields of this reaction. Urea-type intermediates are believed to be generated first in situ from the reaction of o-iodoanilines with heterocumulenes, followed by palladium-catalyzed carbonylation and cyclization to yield the products.

Cycloaddition reaction of 2-vinyloxiranes with carbodiimides using Pd2(dba)3·CHCl3, and TolBINAP as the chiral ligand, in THF at ambient temperature, afforded 4-vinyl-1,3-oxazolidin-2-imines in 70−99% yield and in up to 95% ee. The stereoselectivity is strongly influenced by the structure of the chiral phosphine ligands and substrates, as well as by the reaction conditions. The enantiodetermination step is assumed to be nucleophilic attack of a nitrogen nucleophile on a π-allyl palladium intermediate. Reaction of 2-vinyloxiranes with isocyanates using the same catalyst system afforded 4-vinyl-1,3-oxazolidin-2-ones in high yield but in no greater than 50% ee.

1,3-Oxazines were prepared by palladium−phosphine-catalyzed cycloaddition reactions of vinyloxetanes with heterocumulenes. 4-Vinyl-1,3-oxazin-2-imines were obtained in fine yields by the reaction of 2-vinyloxetanes with carbodiimides in THF at rt for 12 h using 1.5 mol % Pd2(dba)3·CHCl3 and 3 mol % bidentate phosphine ligands (dppe or dppp). When isocyanates were utilized in the reaction, moderate to good yields of 4-vinyl-1,3-oxazin-2-ones were achieved within 1−2 h at rt. Palladium-catalyzed cycloaddition of fused-bicyclic vinyloxetanes with heterocumulenes proceeds in a highly stereoselective fashion affording only the cis-3-aza-1-oxo-9-vinyl[4.4.0]decane derivatives in 43−98% yield.

The first palladium-catalyzed ring-expansion reaction of 2-vinylthiiranes with heterocumulenes to form sulfur-containing five-membered-ring heterocycles is described. This regioselective reaction requires 5 mol % of Pd(2)(dba)(3).CHCl(3) and 10 mol % of bidendate phosphine ligand (dppp, BINAP), at 50-80 degrees C, in THF. The reaction of 2-vinylthiiranes with carbodiimides, isocyanates, and ketenimines affords 1,3-thiazolidine derivatives, whereas the reaction with diphenylketene or isothiocyanates results in the formation of 1,3-oxathiolane or 1,3-dithiolane compounds in good to excellent isolated yields and in up to 78% ee.

4-Vinyl-1,3-oxazoilidin-2-imine derivatives have been synthesized by cycloaddition reactions of 2-vinyloxiranes with unsymmetrical carbodiimides catalyzed by palladium(0) complexes in excellent total isolated yields. After reaction two compounds were always formed, one of which was isolated as the major product. A bulky alkyl group on one of the nitrogen atoms of the carbodiimide enhanced the product ratio in favor of the N-aryl-3-alkyl-1,3-oxazolidin-2-imine. Highly enantioselective cycloadducts (up to >99% ee) were formed by using TolBINAP as the chiral phosphine ligand, in THF at ambient temperatures. The enantiodetermination is believed to be dependent on nucleophilic attack of the anionic nitrogen of the carbodiimide due to the steric interaction of the carbodiimide substituents with the chiral phosphine ligand.