Oxalyl group

This method involves acylation of the primary amine by introducing an acetyl or oxalyl group followed by nitration of the secondary amine so formed in accordance with the reaction (1). The product thus nitrated undergoes alkaline hydrolysis to yield a primary nitramine ... 

Deaminodecarboxylation (Fig. 91) has been observed in Mannich bases 244 having the p-amino acid structure. The reaction, which may be accompanied by side reactions, " takes place regardless of the fact that the carboxy group is estcrified, and even in derivatives pos.sessing the formyl or the oxalyl group. " - ... 

An aminonitroaxylarsinic acid is converted to its oxalyl or similar derivative, the nitro-group then reduced to the amino-group, the latter replaced by hydrogen by aid of the diazo-reaction, and the resulting compound hydrolysed to remove the oxalyl grouping. 

The reaction of diethyl oxalate with ketones in the presence of sodium ethoxide, or other bases, has been used extensively examples are given in Scheme 66. Reaction may occur with esterketone ratios of 1 1, 2 1, or 1 2, but only the 1 1 case finds substantial use in modem synthetic practice. Frequently the a-oxalyl ketone is thermally decarbonylated to give the 3-heto ester.An early example of this was provided by Bachmann s synthesis of equilenin. The mechanism of this reaction has teen examined labeling studies showed that it was the ester carbonyl that was eliminated. The intact oxalyl group has teen used as a directing group in steroid methylation while, more recently, 2-oxalylcyclohexanone has provided a route to (R)-(-)-hexahydromandelic acid (Scheme 67). The products of acylation of suitable acyclic ketones can cyclize to form (enolic) cyclopentane-1,2,4-triones (equation 39). ... 

CziHzzOsNz (XXXIII), from benzaldihydrostrychnine by two methoxyl groups. The i T-oxalyl group of XXXIII is readily cleaved to XXXIV and oxalic acid by warm aqueous barium hydroxide solution. Chromic acid... 

Aromatic polyamides and polyhydrazides containing the oxalyl group... 

Fluorinated ether-containing dicarboxyhc acids have been prepared by direct fluorination of the corresponding hydrocarbon (17), photooxidation of tetrafluoroethylene, or by fluoride ion-cataly2ed reaction of a diacid fluoride such as oxalyl or tetrafluorosuccinyl fluorides with hexafluoropropylene oxide (46,47). Equation 8 shows the reaction of oxalyl fluoride with HEPO. A difunctional ether-containing acid fluoride derived from HEPO contains regular repeat units of perfluoroisopropoxy group and is terminated by two alpha-branched carboxylates. 

Acylation. Acylation is the most rehable means of introducing a 3-substituent on the indole ring. Because 3-acyl substituents can be easily reduced to 3-aLkyl groups, a two-step acylation—reduction sequence is often an attractive alternative to direct 3-aLkylation. Several kinds of conditions have been employed for acylation. Very reactive acyl haUdes, such as oxalyl chloride, can effect substitution directiy without any catalyst. Normal acid chlorides are usually allowed to react with the magnesium (15) or 2inc (16) salts. The Vilsmeier-Haack conditions involving an amide and phosphoms oxychloride, in which a chloroiminium ion is the active electrophile, frequentiy give excellent yields of 3-acylindoles. 

While this work was in progress Spath and Bretschneider showed that strychnine, on oxidation with permanganate in alkaline solution, furnished W-oxalylanthranilic acid (VII), brucine yielding oxalyl-4 5-dimethoxy-anthranilic acid, the latter observation providing confirmation of the evidence previously adduced that the two methoxy-groups in brucine are in the oj Ao-position relative to each other as indicated by Lions, Perkin and Robinson. The results so far considered indicate the presence in brucine and strychnine of the complex (VIII), which can be extended to (IX) if account is taken of the readiness with which carbazole can be obtained from strychnine and brucine and certain of their derivatives by decomposition with alkali at temperatures ranging from 200° to 400°, Knowledge of the structure of the rest of the molecule is mainly due to the results of the exhaustive study by Leuchs and his pupils of the oxidation... 

The mildness of oxalyl chloride permits other sensitive hydroxyl groups ie.g., 5 -OH) to survive without protection. Even the 11 -hydroxyl group has a moderate degree of stability to this reagent. ... 

Many procedures for the formation of carboxylic acid amides are known in the literature. The most widely practiced method employs carboxylic acid chlorides as the electrophiles which react with the amine in the presence of an acid scavenger. Despite its wide scope, this protocol suffers from several drawbacks. Most notable are the limited stability of many acid chlorides and the need for hazardous reagents for their preparation (thionyl chloride, oxalyl chloride, phosgene etc.) which release corrosive and volatile by-products. Moreover, almost any other functional group in either reaction partner needs to be protected to ensure chemoselective amide formation.2 The procedure outlined above presents a convenient and catalytic alternative to this standard protocol. 

This is by far the most used type of primary synthesis for quinoxalines. It usually involves the cyclocondensation of an o-phenylenediamine (or closely related substrate) with a synthon containing an oxalyl [—C(=0)—C(=0)—] or equivalent [e.g., HC(=0)—C=N] grouping. For convenience, discussion of this synthesis is subdivided according to the type of synthon used to produce formally aromatic quinoxalines the formation of similar ring-reduced quinoxalines (mostly from related synthons at a lower oxidation state) is included in each such category. 

DMSO or other sulfoxides react with trimethylchlorosilanes (TCS) 14 or trimefhylsilyl bromide 16, via 789, to give the Sila-Pummerer product 1275. Rearrangement of 789 and further reaction with TCS 14 affords, with elimination of HMDSO 7 and via 1276 and 1277, methanesulfenyl chloride 1278, which is also accessible by chlorination of dimethyldisulfide, by treatment of DMSO with Me2SiCl2 48, with formation of silicon oil 56, or by reaction of DMSO with oxalyl chloride, whereupon CO and CO2 is evolved (cf also Section 8.2.2). On heating equimolar amounts of primary or secondary alcohols with DMSO and TCS 14 in benzene, formaldehyde acetals are formed in 76-96% yield [67]. Thus reaction of -butanol with DMSO and TCS 14 gives, via intermediate 1275 and the mixed acetal 1279, formaldehyde di-n-butyl acetal 1280 in 81% yield and methyl mercaptan (Scheme 8.26). Most importantly, use of DMSO-Dg furnishes acetals in which the 0,0 -methylene group is deuter-ated. Benzyl alcohol, however, affords, under these reaction conditions, 93% diben-zyl ether 1817 and no acetal [67]. 

Quebrachitol was converted into iL-c/j/roinositol (105). Exhaustive O-isopropylidenation of 105 with 2,2-dimethoxypropane, selective removal of the 3,4-0-protective group, and preferential 3-0-benzylation gave compound 106. Oxidation of 106 with dimethyl sulfoxide-oxalyl chloride provided the inosose 107. Wittig reaction of 107 with methyl(triphenyl)phos-phonium bromide and butyllithium, and subsequent hydroboration and oxidation furnished compound 108. A series of reactions, namely, protection of the primary hydroxyl group, 0-debenzylation, formation of A-methyl dithiocarbonate, deoxygenation with tributyltin hydride, and removal of the protective groups, converted 108 into 7. 

The traditional method for transforming carboxylic acids into reactive acylating agents capable of converting alcohols to esters or amines to amides is by formation of the acyl chloride. Molecules devoid of acid-sensitive functional groups can be converted to acyl chlorides with thionyl chloride or phosphorus pentachloride. When milder conditions are necessary, the reaction of the acid or its sodium salt with oxalyl chloride provides the acyl chloride. When a salt is used, the reaction solution remains essentially neutral. 

Another useful method for introducing formyl and acyl groups is the Vilsmeier-Haack reaction.67 /V.A-dialkylamidcs react with phosphorus oxychloride or oxalyl chloride68 to give a chloroiminium ion, which is the reactive electrophile. 

These cyclizations normally involve a carbonyl group. The enamine 109 undergoes a reaction with oxalyl chloride to give an intermediate product 110, which is then cyclized upon treatment with HC1 leading to the angular tricyclic compound 111 in excellent yield (Scheme 11) <1995EJM525>. 

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