Butanoyl chloride acylation with

The tributylstannyl group in 1-phenylsulfonyl-l-tributylstannylcyclopropaneis reactive toward acyl chlorides. When this cyclopropane was refluxed with butanoyl chloride in toluene, 1-butanoyl-l-phenylsulfonylcyclopropane was isolated in 80% yield. 

Another type of Friedel-Crafts reaction also involves a carbocation, but not the simple alkyl carbocations discussed in the previous section. When benzene reacts with butanoyl chloride (49) in the presence of AICI3, the isolated product is a ketone butyrophenone (1-phenyl-l-butanone, 50) in 51% yield. It is known that benzene does not react with 49 without the presence of aluminum chloride. Clearly, the acyl unit has reacted with benzene to form the new carbon-carbon bond, with loss of the chlorine atom of 49, but there must be a prior reaction between AICI3 and the acid chloride. This is an aromatic substitution and, based on knowledge of benzene, there must be an arenium ion intermediate. To form an arenium ion, benzene must react with a cationic species, which must arise from 49. What is the nature of this cationic intermediate ... 

Another category of reductions involves aryl ketones. The Friedel-Crafts acylation reaction reacts benzene with an acid chloride such as butanoyl chloride (49) to give an aryl ketone, 50. Complete removal of the oxygen from this ketone constitutes a method to make straight-chain arenes, which cannot be prepared via Friedel-Crafts alkylation (see Section 21.3.2). At least two classical methods are used to accomplish this reaction, which is formally a reduction. If 50 is treated with zinc metal in HCl, the product is 1-phenylbutane, 105. This acidic reduction involves a mineral acid such as HCl and an active metal, and it is called the Clemmensen reduction. 

The ready reduction of acyl- to alkylarenes also provides a way to synthesize alkyl-benzenes without the complication of alkyl group rearrangement and overalkylation. For example, butylbenzene is best synthesized by the sequence of Friedel-Crafts acylation with butanoyl chloride, followed by Clemmensen reduction. 

Acylation of isobutylbenzene with acetic anhydride leads with high yield and selectivity to para-acetylisobutylbenzene (Eq. 9) which is an intermediate in the synthesis of ibuprofen, an important antiinflammatory drug [18]. With H/1 zeolite at 140 °C after 1 h the yield is 80 % with 96 % para selectivity. Acylation of tetra-lin with acid chlorides and different zeolites has also been studied [19], For this reaction again acetyl chloride is much less reactive than higher acid chlorides such as butanoyl or octanoyl chloride. The selectivity is in favor of the 2-substituted isomer (85-90%) and limited quantities of the 1 isomer (10-15%) are formed (Eq. 10). 

The most prominent cellulose ester produced on the industrial scale is cellulose acetate. The reaction is usually performed with acetic anhydride and with sulfuric acid as a catalyst. To minimize heterogeneities, acetylation is allowed to run nearly to completion, and subsequently partial ester hydrolysis is initiated by the addition of water until a desirable solubility is achieved that corresponds to a DS of about 2.5. Such higher acyl homologues as propanoyl or butanoyl exhibit more thermoplastic properties. Many specialized esters such as chiral (-)-menthyloxyacetates, furan-2-carboxylates, or crown-ether-containing acylates have been prepared on the laboratory scale and characterized by NMR spectroscopy. Various procedures have been applied, using anhydrides and acyl chlorides as acylating agents in combination with such bases as pyridine, 4-dimethylaminopyridine (DMAP), or iV,iV -carbonyldi-imidazole. The substitution pattern of cellulose acetates has also been modified by postchemical enzymatic deacetylation. Cellulose 6-tosylates have been used as activated intermediates for nucleophihc substitution to afford 6-amino-6-deoxy, 6-deoxy, or 6-deoxy-6-halo-celluloses. ... 

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