Michael-type addition of 1,8-diazabicyclo[5.4.0]undec-7-ene to dimethyl acetylenedicarboxylate
作者:Lifu Ma、David Dolphin
DOI:10.1039/c39950002251
日期:——
Michael reaction of DBU 1 with dimethylacetylenedicarboxylate 2 and subsequent intramolecular condensation of the adduct gives a tricyclic derivative 6; a mechanism for the formation of 6 is proposed and an X-ray crystal structure of 6 is presented.
The reactions of potassium 2-indolizinethiolates having an ester group at the 3-position with some electron deficient acetylenic compounds were investigated. Their Michael additions or Michael addition-cyclizations proceeded with the elimination of an ester group to provide the corresponding 2-vinylthioindolizine and 4H-thiino[2,3-b]indolizin-4-one derivatives.
Photooxygenation of 5-Dialkylamino-4-pyrrolin-3-ones. Synthesis of Highly Functionalized Ureas, 2-Oxazolidinones, and 2-Oxazolinones
5-Dialkylamino-4-pyrrolin-3-ones, available from cyclocondensation of amidines with dimethylacetylenedicarboxylate (DMAD), undergo rapid singlet oxygenation to give highly functionalized ureas by way of a 1,2-dioxetane cleavage of the initially formed [2 + 2] cycloadducts. These latter compounds undergo cyclization to 2-oxazolidinones in MeOH. Catalytic hydrogenation of the ureas in EtOAc gives 2-oxazolinones