Oxalyl chloride-Sodium iodide

Ketoester 208 derived from l-(2-nitrophenyl)-lH-pyrrole and ethyl oxalyl chloride can be selectively reduced at the keto group with zinc iodide and sodium cyanoborohydride. Further reduction of the nitro group and cyclization to lactam 209 has been accomplished by treatment with stannous chloride in refluxing ethanol (Scheme 43 (2003BMCL2195)). 

Another total synthesis of sufentanil has been described the cyclization of 2-(2-thienyl)ethylamine with allyl-trimethylsilane and formaldehyde gives 4-hydroxy-1-[2-(2-thienyl)ethyl]piperidine, which is oxidized with oxalyl chloride in DMSO/dichloromethane to 1-[2-(2-thienyl) ethyl]piperidin-4-one. The epoxidation of this compound by means of trimethylsulfonium iodide and the sodium salt of DMSO yields the spiro-epoxide, which is opened with... 

Interchange of halogen is a means of synthesis of certain acyl halides which cannot be conveniently prepared by other methods. Acetyl fluoride is made from acetyl chloride and sodium hydrogen fluoride in acetic anhydride solution." By passing a stream of hydrogen bromide through oxalyl chloride an 85% yield of oxalyl bromide, (COBr), is obtained. The bromide cannot be made by the action of phosphorus pentabromide on oxalic acid. The method has also been applied to the preparation of acetyl bromide and iodide and other acyl iodides. ... 

DIBAL-H/n-butyllithium, in cyclic and acyclic systems with iron pentacarbonyl, in cyclodecanes with lithium dihydrodimethoxyaluminate(III)/copper(I) iodide, and in cyclohexane and cyclopentane systems with NaH/sodium r-butylpentyl/Ni(OAc)2. ° The monoreduction of 1,3-diketones can be carried out under similar conditions, as illustrated by the reaction of a substituted cyclohexane-1,3-dione with oxalyl chloride to give the corresponding 1-chlorocyclohexenone, which was subsequently reduced to the enone with zinc-silver couple (Scheme 45). Kropp et al. have reported the photolytic reduction of vinyl iodides in acyclic systems however, when an a-hydrogen is present, formation of the diene product is a limiting side reaction (Scheme 46). For a more extensive discussion of vinyl halide reductions, see the preceding chapter in this volume. 

Complex (+)-218 was prepared from 148 as illustrated in Scheme 31. The reaction of 148 with Fe(CO)s followed by I2 afforded complex 215 <2002AGE174>. Selective reduction of this iodide with sodium amalgam followed by reaction with TMSCl gave 216. Hydrolysis of 216 followed by resolution using chiral HPLC afforded (—)-217 for which an X-ray stmcture has been obtained. This hydroxyl compound was then sequentially converted to chloride (—)-216 using oxalyl chloride and tosylate (-f)-218 using AgOTs. 

Another synthesis of homoharringtonine was reported by Wang et al. 49-51) in 1980 (Scheme 21). Treatment of the sodium salt 154 of the protected keto acid with oxalyl chloride, followed by cephalotaxine, gave the cephalotaxyl ester 155, which, under Reformatsky conditions, reacted with methyl bromoacetate to furnish the expected diastereomeric mixture of ketals 156. Hydrolysis of 156 yielded an equilibrium mixture of ketone 157 and its cychc hemiketal 158. Treatment of this mixture with methyl-magnesium iodide yielded homoharringtonine (3) and its epimer. 

Additive Pummerer reactions of the type described above using racemic a,P-unsaturated sulfoxides can be accomplished using the following electrophiles acyl chlorides [205,206], dithioacetic acid [207], acetic anhydride [208], mineral acids/alcohols [209], phosphorus pentachloride [210], silyl ketene acetals/zinc iodide [211], thionyl chloride [212], oxalyl chloride [213], trifluoroacetic acid and its anhydride [214-218], triflic anhydride/sodium acetate [219], and dichloroketene (see below). Selected recent examples of work in this area are presented here. 

Esterification.—iVAWW -Tetramethylchloroformamidinium chloride, which is readily prepared from iVAWW -tetramethylurea and oxalyl chloride, is an efficient reagent for the esterification of carboxylic acids with alcohols yields of between 66 and 97% are obtained, and the method has also been applied to macrolide synthesis. A modified one-pot procedure for the esterification of carboxylic acids, using phenyl dichlorophosphate-dimethylformamide complex, has appeared. A simple method of activation of carboxylic acids, using methanesulphonyl chloride and triethylamine followed by addition of the alcohol and 4-dimethylaminopyridine, leads to esters in 57— 96% yield for thirteen examples. 0-Methylcaprolactim reacts with carboxylic acids to give methyl esters in 73—91 % yield for seven examples and 2-iodoethyl esters are prepared from acyl chlorides, ethylene oxide, and sodium iodide. Transesterification, catalysed by titanium(iv) alkoxides, provides an effective method for synthesis of esters. Diethyl trichloromethylphosphonate reacts with carboxylic acids to give ethyl esters via transesterification, in 52 to 98 % yield. ... 

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