Selective syntheses of 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones via temperature-dependent Rh(II)-carbenoid-mediated 2H-azirine-ring expansion

Add time:07/31/2019    Source:sciencedirect.com

The Rh(II)-catalyzed reaction of 2-carbonyl-substituted 2H-azirines with ethyl 2-cyano-2-diazoacetate or 2-diazo-3,3,3-trifluoropropionate provides an easy access to 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones. These compounds can be selectively prepared from the same starting material using temperature as the only varied parameter. The 2-azabuta-1,3-diene intermediate, a common precursor for both heterocyclic products, isomerizes into 2H-1,3-oxazine under kinetic control, while 1H-pyrrol-3(2H)-one is the sole product of the reaction at elevated temperatures. According to DFT-calculations a one-atom oxazine ring contraction involving ring-opening to a 2-azabuta-1,3-diene intermediate, followed by a 1,5- and 1,2-prototropic shift leads to the consecutive formation of imidoylketene and azomethine ylide, which then further undergo cyclization to the pyrrole derivative.

We also recommend Trading Suppliers and Manufacturers of 2H-1,3-Oxazine-3(4H)-carboxylic acid, 2-oxo-, ethyl ester (cas 126972-53-0). Pls Click Website Link as below: cas 126972-53-0 suppliers

Prev:The actin binding cytoskeletal protein Moesin is involved in nuclear mRNA export
Next:Flavonoid conformational analysis: comparison of the molecular structures of (Z)-4,4',6-triacetoxyaurone and (Z)-3',5'-dibromo-2',4,4',6-tetrahydroxyaurone monohydrate by crystallographic and molecular orbital methods)