PALLADIUM(II)-CATALYZED INTRAMOLECULAR AMINOCARBONYLATION OF ENDO-CARBAMATES UNDER WACKER-TYPE CONDITIONS

Pd(II)-catalyzed intramolecular aminocarbonylation of olefins bearing many types of nitrogen nucleophiles has been examined under two typica l conditions: acidic conditions [conditions A, typically PdCl2 (0.1 eq uiv) and CuCl2 (3.0 equiv) under 1 atm of CO at room temperature in me thanol] and buffered conditions [conditions B, typically PdCl2 (0.1 eq uiv) and CuCl2 (2.3 equiv) under 1 atm of CO at 30 degrees C in trimet hyl orthoacetate]. Among nitrogen nucleophiles, endo-carbamates 7 disp lay distinctive reactivity: endo-carbamates 7a-k smoothly undergo intr amolecular aminocarbonylation under conditions B to furnish 4-[(methox ycarbonyl)methyl]-2-oxazolidinones 8a-k in good yields, while they wou ld not undergo the expected reaction under conditions A. Other nitroge n nucleophiles (exo-ureas 1, endo-ureas 3, exo-carbamates 5, and exo-t osylamides 9), on the other hand, satisfactorily undergo aminocarbonyl ation only under conditions A to give rise to 2, 4, 6, and 10, respect ively, in good yields. Under conditions B, they are unreactive and pro vide either the expected products in poor yields or intractable mixtur es of products. On the basis of this contrasting reactivity between en do-carbamates and other nitrogen nucleophiles, the chemoselective amin ocarbonylation of 7l-o has been achieved; aminocarbonylation takes pla ce at the endo-carbamate moieties to furnish 8l-o exclusively under co nditions B, and aminocarbonylation occurs at the exo-carbamate, exo-ur ea, and exo-tosylamide moieties to yield 13a-d exclusively under condi tions A.