Preparation and Reactions of Acid Chlorides

PRACTICE the skill 21.14 Propose a plausible mechanism for each of the following transformations. These reactions will all appear later in this chapter, so practicing their mechanisms now will serve as preparation for the rest of this chapter 

16 Propose a plausible mechanism forthe following intramolecular transformation  

8 Preparation and Reactions of Acid Chlorides Preparation of Acid Chlorides 

Acid chlorides can be formed by treating carboxylic acids with thionyl chloride (SOCl,) O O 

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This chapter concerns the preparation and reactions of acyl chlorides acid anhydrides thioesters esters amides and nitriles These com pounds are generally classified as carboxylic acid derivatives and their nomenclature is based on that of carboxylic acids... 

Lactams are readily prepared by reaction of acid chlorides or bromides with imines in the presence of a tertiary base, usually triethylamine. The method is extremely versatile. Conditions are very mild (inert solvent, room temperature) and sensitive functional groups are tolerated on both the imine and acid chloride partners (equations 2 l-W). " ... 

Ketone synthesis. Ketones can be prepared by reaction of acid chlorides and organotin compounds in HMPT catalyzed with 1 (equation 1). The synthesis has... 

Petoxycatboxyhc acids also have been prepared by the reaction of acid chlorides, anhydrides, or boric-catboxyhc anhydrides with hydrogen or sodium peroxide. These reactions ate carried out at low temperature and with excess peroxide to avoid the formation of diacyl peroxides (44,168,181,184). 

Conversion of Acid Halides into Amides Aminolysis Acid chlorides react rapidly with ammonia and amines to give amides. As with the acid chloride plus alcohol method for preparing esters, this reaction of acid chlorides with amines is the most commonly used laboratory method for preparing amides. Both monosubstituted and disubstituted amines can be used, but not trisubstituted amines (R3N). 

Carbon-phosphorus double bonds are also formed in addition reactions of tris(trimethylsilyl)phosphine 1692 (which can be readily prepared from white phosphorus, sodium, and TCS 14 [13a,b,c]) to give oxazohum fluorides 1691 which then give the azaphospholes 1694, via 1693 [3, 14]. On addition of 1692 to 1695, the diazaphosphole 1696 [3, 15] is prepared, whereas l,3-azaphospholo[l,2a]pyridines 1698 [16] are formed from 1692 and 1697, and 1,3-thiaphospholes 1700 are formed from the dithiohum fluorides 1699 [17]. l,3-Benzodiphospholyl anions 1703 are generated by reaction of acid chlorides with the dihthium salts 1701, via 1702 [18] (Scheme 11.3). 

Preparation and Properties of Chromyl Chloride, a. Put a mixture of 1 g of sodium chloride with 1 g of potassium dichromate into a dry test tube, add a few drops of concentrated sulphuric acid, and close the tube with a stopper provided with a gas-discharge tube. Lower the other end of the latter into another dry test tube submerged in a beaker with cold water. Slightly heat the reaction mixture. What collects in the receiver Write the equations of the reactions. 

The procedure may be adapted for the preparation of other acyl isocyanates (i.e., dichloroacetyl, trichloroacetyl, phenyl-acetyl, diphenylacetyl, benzoyl, etc) and is generally more convenient than the reaction of acid chlorides with silver cyan-ate3 4 Acyl isocyanates react with amines, alcohols, and mer-captans to yield acyl ureas, carbamates, and thiocarbamates. 

The reagent is prepared by reaction of sulfuryl chloride with imidazole. It is hydrolyzed by acid only at elevated temperatures, and does not react with carboxylic acids to form imidazolides.1... 

Phthaloylation of tertiary amines and amino acids is rapidly effected by reaction with 3-chloro-3-(dimethoxyphosphoryl)isobenzofuran-l(3//)-onet a stable, crystalline reagent (mp 78-80 °C) easily prepared by reaction of phthaloyl chloride with trimethyl phosphite [Scheme 8.13] 25 The reaction can be performed in aqueous media and the dimethyl phosphite by-product of the reaction is water soluble. 

Modified Curtius rearrangement. Acyl azides, preferably prepared in situ under phase-transfer conditions by reaction of acid chlorides and NaN, are converted to tri-fluoroacetamides by reaction with CF,COOH in refluxing CH CI, solution. These products are cleaved to primary amines under mild conditions (equation I). ... 

A second, more versatile, method involves the O-acyl thiohydroxamates. These compounds are generally prepared by reaction of acyl chlorides with the commercial sodium salt (1) of 2-mercapto-pyridine A(-oxide (equation 6 X = Cl). Use of mixed anhydrides formed by reaction of the carboxylic acid with isobutyl chloroformate (equation 6 X = OCC>2CH2CHMe2) renders the procedure compatible with unprotected indoles, phenols, secondary and, presumably, tertiary alcohols. An alternative mode of preparation of the 0-acyl thlohydroxamates involves the s t (2) in reaction with the carboxylic acid (equation 7). 

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