Diazo esters, reduction

Claisen ester condensation, 6, 279 Thiazolecarboxylic acid chlorides reactions, 6, 279-280 Thiazolecarboxylic acid hydrazides synthesis, 6, 280 Thiazolecarboxylic acids acidity, 6, 279 decarboxylation, 6, 279 reactions, S, 92 6, 274 Thiazole-2-carboxylic acids decarboxylation, S, 92 Thiazole-4-carboxylic acids stability, S, 92 Thiazole-5-carboxylic acids decarboxylation, S, 92 Thiazole-4,5-dicarboxylic acid, 2-amino-diethyl ester reduction, 6, 279 Thiazole-4,5-dicarboxylic acids diethyl ester saponification, 6, 279 Thiazolediones diazo coupling, 5, 59 Thiazoles, 6, 235-331 ab initio calculations, 6, 236 acidity, S, 49 acylation, 6, 256 alkylation, S, 58, 73 6, 253, 256 analytical uses, 6, 328 antifogging agents... 

Non-functionalized aliphatic diazo compounds are fairly rare, and so are their reductions. Good examples of the reduction of diazo compounds to either amines or hydrazones are found with a-diazo ketones and a-diazo esters (pp. 124, 125, 160). 

Catalytic reduction of 235 produced the chiral hydroxypyrrolidine 236 in yield. When the (Z) alkene 232 was subjected to a similar sequence, the diazo ester 237 was obtained directly in 65% yield. Catalytic hydrogenation of the diazo ester 237 afforded the corresponding chiral hydroxypyrrolidine 238 in 91% yield. 

As may now be expected from Cu(II) compounds, whose reduction to Cu(I) is a requirement for catalyst activation, product yield and enantioselectivity depend on the reagents and conditions used. Other diazo carbonyl compounds, including a (J-keto-a-diazo esters and oc-diazo esters, underwent intramolecular cyclopropanation in moderate-to-good yields, but with low enantiocontrol. 

The reaction is carried out at ambient temperature and nearly complete enantioselectivity (>99%) is observed for mono- and 1,1-disubstituted olefins with diazoacetates. With all copper catalysts, the transkis selectivities in the cyclopropanation of mono-substituted olefins are only moderate. The transkis ratio depends, in this case, mainly on the structure of the diazo ester rather than the chiral ligand (eq 2). It increases with the steric bulk of the ester group of the diazo compound. With the BHT ester, the more stable trans isomer is formed with selectivities up to >10 1. The steric hindrance usually prevents ester hydrolysis, but the BHT group can be removed by reduction with LiAlHj. The trans isomer is even enriched by the reduction procedure because the cis isomer reacts more slowly. 

In close structural analogy to the semicorrinate ligands of 9, the bidendate, chiral C2-symmetric 5-azasemicorrins 10216 and bis(4,5-dihydrooxazol-2-yl)methane systems li,196 217 12,218 219 12a,197 13,220 and I4197a perform exceptionally well in copper-catalyzed enantioselective cyclo-propanation reactions with diazo esters. With 10, 11, and 12 a, the active catalyst is prepared in situ by adding a catalytic amount of a copper(I) salt with a weakly coordinating anion [copper(I) triflate,196,217,219 copper(I) perchlorate197] to the free ligand with the enolizable system 12 (as well as with 12a and 14) it has been prepared by reaction with copper(I) terh butoxide or from the copper(I) bischelate complex by reduction with phenylhydrazine. 

Reduction of a,p-unsaturated y-lactones to furanes (1,262). Pelletier et al. have developed a general method for conversion of 2(5H)-furanones (1) into substituted furanes (4). The method involves cycloaddition of diazoalkanes, diazo esters, and diazoketones, followed by decomposition to alkylated 2(5H)-furanones (3). The final step involves reduction with diisobutylaluminum hydride. 

EC oxidation is commonly employed in the analysis of some basic drugs, especially morphine and related opioids (Chapter 6, Section 1). Even if a compound is not amenable to EC oxidation, its metabolites may be. Phase I metabolism of aromatic xenobiotics often proceeds with aromatic hydroxylation. Hydrolysis of phenolic esters, reduction of diazo double bonds to primary amines and other reactions also occur. EC detection is not widely used to measure acidic or neutral compounds, such as salicylate or paracetamol after overdosage, since these compounds, although easily oxidised, are normally present at relatively high concentrations and UV detection is adequate. However, EC methods may be useful in measuring the plasma concentrations of these compounds attained after a single oral dose. ... 

It is a useful reagent for orthoester homologation via dialkoxy-carbenium ions and for oxazole formation by reaction of keto-carbenes (via diazo esters/Cu(OTf)2) with nitriles (eq 10). With unsaturated nitriles, the nitrile group is selectively attacked. Kinetic and ESR evidence shows that Cu Cu reduction is the key step. ... 

Reductions of halogen, nitro, diazo and azido derivatives of esters resemble closely those of the corresponding derivatives of carboxylic acids (p. 141). 

Types of compounds are arranged according to the following system hydrocarbons and basic heterocycles hydroxy compounds and their ethers mercapto compounds, sulfides, disulfides, sulfoxides and sulfones, sulfenic, sulfinic and sulfonic acids and their derivatives amines, hydroxylamines, hydrazines, hydrazo and azo compounds carbonyl compounds and their functional derivatives carboxylic acids and their functional derivatives and organometallics. In each chapter, halogen, nitroso, nitro, diazo and azido compounds follow the parent compounds as their substitution derivatives. More detail is indicated in the table of contents. In polyfunctional derivatives reduction of a particular function is mentioned in the place of the highest functionality. Reduction of acrylic acid, for example, is described in the chapter on acids rather than functionalized ethylene, and reduction of ethyl acetoacetate is discussed in the chapter on esters rather than in the chapter on ketones. 

Hydrolysis of enol esters 0-76 Reduction of halo ketones 0-78 Reduction of hydroxy ketones 0-82 Reduction of diazo ketones or nitro ketones... 

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