Nitronic acid esters, cyclic

Nitronic acid esters, cyclic s. 4H-l,2-Oxazine 2-oxide ring, 5,6-dihydro-Nitronitiic acid esters... 

The chemistry of a-haloketones, a-haloaldehydes and a-haloimines Nitrones, nitronates and nitroxides Crown ethers and analogs Cyclopropane derived reactive intermediates Synthesis of carboxylic acids, esters and their derivatives The silicon-heteroatom bond Syntheses of lactones and lactams The syntheses of sulphones, sulphoxides and cyclic sulphides... 

Cyclic nitrones 1490 (A -imidazoline 3-oxides) react regioselectively with alkyl phenylpropiolates 1491 (or with dimethyl acetylenedicarboxylate) to give the corresponding 2-phenyl-3a,4,5,6-tetrahydroimidazo[l,5- ]isoxazole-3-carboxylic acid alkyl esters 1492. Subsequent thermal, base (piperidine, triethylamine, or alkoxide) induced ringopening reactions led to imidazoles 1493 (Scheme 385) <2004SC1617, 2000TL5407>. 

Quinoxaline-2-carboxaldehyde has been converted into the 2-carboxylic acid by oxidation with potassium permanganate in acetone and reduced to the 2-hydroxymethyl compound by treatment with formalin and potassium hydroxide. It also undergoes other typical reactions of aromatic aldehydes such as benzoin formation on reaction with potassium cyanide - and condensation reactions with malonic acid and its diethyl ester and Schiff base formation. Acid-catalyzed reaction of quinoxaline-2-carboxaldehyde with ethylene glycol gives the cyclic acetal the diethylacetal has been prepared by reaction of 2-dibromomethylquinoxaline with sodium ethoxide. " An indirect preparation of the oxime 11 is achieved by treatment of 2-nitromethyl-quinoxaline (10) with diazomethane followed by thermolysis of the resulting nitronic ester. 

Racemic cocaine (8) was stereospecifically synthesized by cycloaddition of the ( ) olefinic carboxylic acid nitrone (6) via the cyclic hydroxylamine (7). None of the previous approaches to cocaine had the advantage of this stereospecificity since they involved the reduction of an ecgoninone ester, i.e. a /8-keto-ester, which gave a mixture of diastereoisomers, these being the 2 S,3/3-(8), which was... 

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