Zinc chloride acetic anhydride reagent

Alkenes react with acyl halides or acid anhydrides in the presence of Lewis acid catalysts. The reaction works better with cyclic alkenes than for acyclic ones. A mechanistically significant feature of this reaction is the kinetic preference for formation of unsaturated ketones. Mechanistic studies using acetic anhydride and zinc chloride as the reagent system are consistent with a two-step mechanism in which the location of the double bond in the product is determined by ease of deprotonation of the initial adduct. A related reaction occurs when alkenes react... 

Tosylhydrazones on reaction with alkylithium reagents give olefins in high yield. This new synthesis allowed for exas le the preparation of 16-androstene from androstan-17-one in quantitative yield.Reduction of carbonyl functions to methylene c ui be effected electrochemically or by treatment of the steroid ketones with powdered zinc in acetic anhydride saturated with hydrogen chloride at room temperature." ... 

Gansauer, and a titanocene complex, TiCl3(THF)3, is also applicable as disclosed by Nelson and co-workers Catalytic pinacol coupling reactions occur with TiCU and zinc (or aluminum) in the presence of an acylating reagent such as acetic anhydride or acetyl chloride. ... 

Diethyl ethylidenemalonate has been prepared by heating acetaldehyde, diethyl malonate, and acetic anhydride 2 3 by heating the same reagents plus zinc chloride 4 by treating acetaldehyde and diethyl malonate with sodium ethoxide or piperidine 6 and by heating diethyl malonate, ethylidene bromide, and ethanolic sodium ethoxide.6... 

Solvated perfluoroalkyl zinc reagents have been prepared by reaction of perfluoroalkyl iodides with zinc in ethereal solvents such as dioxane [36,37]. Self-coupled and cross-coupled products can be formed when a mixture of acetic anhydride and methylene chloride was used [38-40] (Scheme 11). 

The effect of a Lewis acid on the o-nitro-(-aniline system is well illustrated by the unexpected result from the attempted Friedel-Crafts acetylation of these compounds. In 1926, van Romburgh and co-workers51,52 observed that the action of acetic anhydride and zinc chloride on the o-nitrodimethylaniline (111) did not give the acetylated product (112), but instead the benzimidazolone (113). Even more surprising was their alleged observation that the same reagents converted the diethyl compound (114) into the quinoxaline... 

A new aromatization of ring c has been achieved by treating the 16a, 17a-epox ypregn-8-ene-7,ll,20-trione system (277) with zinc chloride in acetic anhydride.227 The product (278) was accompanied by the diene-trione (279). Use of other acidic reagents, or of the 7-deoxy-analogue of compound (277), failed to give an aromatic product. 

With anhydrides, aluminum chloride reacts to form the acid chloride complex. Zinc chloride is more commonly used with acid anhydrides, although this is restricted practically to acetic and other simple anhydrides that can be used as the reaction solvent. This nevertheless remains a useful reagent for acylations, giving predominantly nonconjugated products. Active zinc compounds prepared from a zinc-copper couple and alkyl halides also promote the acylation of alkenes by acyl chlorides at room temperature. ... 

Acetic anhydride and aluminum chloride in caibon disulfide gives a high yield of the para-acylated product with thioanisole, and in dichloromethane the same reagents give an almost quantitative yield of 3-acetyl-1-benzenesulfonylindole. Acylation of more nucleophilic heterocycles can be achieved using milder catalysts, such as zinc chloride. It has been known for some time that furan can be acylated very efficiently using acetic anhydride and zinc chloride. The Paal-Knorr furan synthesis (1,4-diketone, acetic anhydride and zinc chloride) can sometimes result in acylation as well as cyclization (equation 40). - Equations (41) and (42) further exemplify the acylation of furan derivatives that have been used in the synthesis of cytotoxic furanonaphthoquinones. 

Anjaneyulu, A. S. R., Mallavadhani, U. V., Venkateswarlu, Y., and Ramaprasad, A. V. 1987. Reaction of acetic anhydride/zinc chloride reagent with phenols improved yields of hydroxyacetophenones. Ind. J. Chem. 26B 823-826. 

One of the earliest examples was the isolation of an unexpected pentaacetate after treatment of 1,2-0-isopropylidene-a-D-glucofuranose with acetic anhydride and zinc chloride. These reagents had effectively produced the acetylium ion (8). The product was subsequently character-... 

Reagents i, Sodium borohydride, 2,2,2-trichIoroethyl chloroformate, t-butylglyoxylic acid ii, thionyl chloride, triphenylphosphine and pyridine, zinc in aqueous acetic acid iii, dimethyl sulphoxide and acetic anhydride... 

The use of zinc chloride and related substances, or acetic anhydride, is a common feature of many reactions of alkylpyridines. The first type of reagent probably exercises a generalized acid catalysis, augmenting the reactivity of alkyl groups by coordination with the nitrogen atom. Acetic anhydride... 

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