Aminocarbonylation of N-2-propenyl-1, N-3-butenyl-4, and N-4-pentenylureas 8 proceeds smoothly under the Wacker-type conditions (cat. PdCl2, stoichiometric CuCl2, 1 atm of carbon monoxide at 0 °C - r.t.) and furnishes 2-imidazolidinone 4-acetic acids 2, tetrahydro-2-pyrimidinone 4-acetic acids 5 and bicyclic dihydrouracils 10, respectively, in good yields. Bicyclic pyrrolidine lactones 15 and piperidine lactones 18 are obtained under the similar conditions, endo-Carbamates 21 display completely different reactivity from exo-carbamates (e.g., 8', R=CO2Me), through which the chemoselective cyclization of 23 (e.g., R=CO2Me) either at the endo-carbamate moiety (providing 24, R=CO2Me) or at the exo-carbamate moiety (providing 25, R=CO2Me) is achieved only by changing the reaction medium (the former in trimethyl orthoacetate and the latter in methanol). 4-(1-Methoxycarbonylvinyl)-1,3-oxazolidin-2-ones 27 and -tetrahydro-1,3-oxazin-2-ones 29 are obtained in good yields under the similar conditions optimized for endo-carbamates 21. The nitrogen atom of 0-propargyl carbamates 31 add intramolecularly to the triple bond to furnish 4-alkylidene-1,3-oxazolidin-2-ones 32 by the catalysis of CuCl•Et3N. Similarly, CuCl•Et3N promotes the aminocyclization of biscarbamate 33 to provide 32 (R2=CH2OCONHTs), while Pd2(dba)3•CHCl3 selectively promotes the cyclization to furnish 34, the C2-C3 double bond of which undergoes a [2+2] cycloaddition with phenylacetylene and methyl acrylate. The enamine double bond reacts with methyl vinyl ketone and acrolein to provide [2+4] addition products. Allene carbamates 38 and 40 undergo cyclization to provide 4-vinyl-1,3-oxazolidin-2-ones 39 and 4-vinyltetrahydro-1,3-oxazin-2-ones 41, respectively, by the catalysis of Ag+•Et3N. The structurally related 43 (R=aryl, sulfonyl) are also obtained with high stereoselectivity by the reaction of cyclic carbamates 42 and isocyanates under the catalysis of Pd(PPh3)4. Allylic aminoalcohols derived from carbamates 39, 41, and 43 are utilized as probes to elucidate the electronic effects of the allylic amino and allylic hydroxyl groups on the stereoselective and/or regioselective cyclization reactions: Cope rearrangement (eq 21), endo-trig cyclization (eq 22), and iodoetherification (eq 23). Making contrast to the Ag+•Et3N catalyzed protioaminocyclization of 38 (eq 16), by the catalysis of Pd(PPh3)4, 0-2,3-butadienyl carbamates 55' undergo (2,3-butadien-2-yl)aminocyclization to provide 58. PdCl2, in the presence of an allylating agent (a large excess), promotes the allylaminocyclization of 55 and furnishes trans-56 in good yields and with excellent stereoselectivity.
amination - aminocarbonylation - C-C multiple bonds - urea - carbamate
