Palladium-catalyzed cycloaddition reaction of 2-vinyloxiranes, 2-vinyloxetanes, o-iodophenols and o-iodoanilines with heterocumulenes. The efficient methods for the preparation of heterocyclic compounds.

Abstract

A study of heterocyclic formation by cycloaddition reactions has been made utilizing 2-vinyloxiranes, 2-vinyloxetanes, o-iodophenols and o-iodoanilines with heterocumulenes in the presence of a palladium catalyst. Cycloaddition reactions of 2-vinyloxiranes with carbodiimides using Pd2(dba)3·CHCl3 and TolBINAP in THF, at ambient temperature, afforded 4-vinyl-1, 3-oxazolidin-2-imines in 70--99% yields 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. Reaction of 2-vinyloxiranes with isocyanates using the same catalyst system afforded 4-vinyl-1, 3-oxazolidin-2-ones in high yields but no greater than 50% ee under identical conditions. The cycloaddition reactions of 2-vinyloxiranes with unsymmetrical carbodiimides catalyzed by palladium(0) complexes gave two isomers of 4-vinyl-1, 3-oxazolidin-2-imine derivatives in excellent total isolated yields. Highly enantioselective cycloadducts (up to >99% ee) were formed by using TolBINAP as the chiral phosphine ligand, in THF at ambient temperatures. 4-Vinyl-1, 3-oxazine-2-imines were obtained in fine yields by the reaction of 2-vinyloxetanes with carbodiimides catalyzed by Pd2(dba) 3·CHCl3 and bidentate phosphine ligands (dppe or dppp). When isocyanates were utilized in the reaction, moderate to good yields of 4-vinyl-1, 3-oxazine-2-ones were achieved. 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. Benzo[e]-1,3-oxazin-2-imine-4-ones were synthesized regioselectively by cyclocarbonylation of o-iodophenols with carbodiimides in the presence of a catalytic amount of palladium catalyst and 1,4-bis (diphenylphosphino) butane under CO pressure. Product yields are dependent on the nature of the substrate, catalyst, solvent, and base as well as phosphine ligand. Benzo[e]-1,3-oxazin-2,4-diones were obtained in good-excellent yields using the same procedure, and a 1:2 ratio of o-iodophenol: isocyanate. Pyrido[3,2-e]-1,3-oxazin-4-ones were isolated in fine yield using 2-hydroxy-3-iodopyridine. A catalyst system comprising palladium acetate-bidentate phosphine is effective for the cyclocarbonylation of o-iodoanilines with heterocumulenes to give the corresponding 4(3H)-quinazohn-4-one derivatives in good yields. Utilizing o-iodoanilines with isocyanates, carbodiimides and ketenimines for the reaction afforded 2,4-(1 H,3H)-quinazolinediones, 2-amino-4(3H)-quinazolinones and 2-alkyl-4(3H)-quinazolinones, respectively. In the last Chapter, a study on the one-pot reaction of o-iodoanilines with acid chlorides and carbon monoxide showed that in the presence of a palladium catalyst and a base, the pharmaceutically important compounds, 2-substituted-4 H-3,1-benzoxazin-4-ones, could be isolated in high yields.