Y-Nitro ester

Earlier, the reduction of y-nitro esters with zinc and ammonium chloride had been shownto provide a suitable route to A-hydroxy 2-pyiTolidones, e.g., 42. Various catalytic hydrogenation procedures can also effect the same reductive cyclization. ... 

Bicyclic ester 100 forms in analogy to isomeric ester 65 (Section 2.4.1.1) (07JOC5608). /l-Phenylethylamine 101 undergoes palladium-catalyzed direct aromatic carbonylation, thus providing another synthesis of benzo-lactam 78b (06JOC5951). A stereoselective nitro-Mannich/lactamization cascade of y-nitro ester and cyclic imine affords polysubstituted lactam 102 (08OL4267). 

Intramolecular retro-Michael disconnection of the y-nitro ester and opening of the cyclohexane ring provide an innovative retrosynthetic concept. Next, retro-Michael disconnection splits the aromatic unit from the unsaturated nitro ester. 

Cobb and coworkers reported another intramolecular Michael addition of conjugated esters 117. They screened a range of thiourea catalysts and found bifunc-tional compound 116 gave sahsfactory results in this cycHzation, furnishing the cyclic y-nitro esters 118 with up to three stereocenters (Scheme 36.32) [40]. 

METHYL y-METHYL-y-NITROVALERATE (Isocaproic acid, Y-nitro, methyl ester)... 

Reaction of the Titanated Bislactim Ether. The titanium derivative of the bislactim ether of cyclo(L-Val-Gly) reacts with alkyl aldehydes, aryl aldehydes, and a,(3-unsaturated aldehydes highly diastereoselectively to give almost exclusively the syn addition products (eq 2). Hydrolysis with dilute Trifluo-roacetic Acid affords (2R, 35 )-(3-hydroxy-a-amino acid methyl esters. a-Amino-y-nitro amino acids can be obtained by 1,4-addition of the titanated bislactim ether to nitroalkenes and subsequent hydrolysis of the adduct. ... 

In the base-induced cyclization of a number of y-chloro-y-nitro carboxylic esters and derivatives, it was found that use of excess base led to elimination of nitrous acid resulting in methylenecyclopropanes. Thus, reaction of ethyl 4-chloro-4-nitropentanoate (1) with one equivalent of sodium hydride in dimethylformamide gave, in addition to a 53% yield of ethyl 2-methyl-2-nitrocyclopropanecarboxylate(2), 12% of ethyl 2-methylenecyclopropanecarboxylate (3). The latter could be prepared in 70% yield from the former, or in 55% yield from the starting ester by the use of two equivalents of sodium hydride. 

P-Ketoesters. /3,y-Unsaturated )3-nitro esters undergo reductive Nef reaction in the presence of Raney nickel and sodium hypophosphite in a buffered medium. 

This successful 1,4-addition of nitromethane anion and the subsequent chemical manipulation of the nitro ester derivatives opens the way to new series of sugar y-amino acid building blocks like compound 61 which are of interest in the context of glycofoldamers synthesis. ... 

A fairly general route to y-keto-esters consists of a coupling reaction between nitro-ethylenes and O-silyl ester enolates (Scheme 18) under well-established conditions [TiCl4-Ti(OPr 4)-CH2Cl2, -78 Yields are good with simpler... 

Conjugate addition of keten methyltrimethylsilylacetal to nitro-olefins is also possible using TiCl4-Ti(Pr 0)4 as a catalyst. After hydrolysis and treatment with diazomethane the product of the reaction is a y-keto-ester (Scheme 15). ... 

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