Chlorides, acyl, also

Carboxylic acid anhydrides compounds of the type RCOCR can also serve as sources of acyl cations and m the presence of aluminum chloride acylate benzene One acyl unit of an acid anhydride becomes attached to the benzene ring and the other becomes part of a carboxylic acid... 

Stannic chloride is also used widely as a catalyst in Eriedel-Crafts acylation, alkylation and cycHzation reactions, esterifications, halogenations, and curing and other polymerization reactions. Minor uses are as a stabilizer for colors in soap (19), as a mordant in the dyeing of silks, in the manufacture of blueprint and other sensitized paper, and as an antistatic agent for synthetic fibers (see Dyes, application and evaluation Antistatic agents). 

Another route to enantiomcrically pure iron-acyl complexes depends on a resolution of diastereomeric substituted iron-alkyl complexes16,17. Reaction of enantiomerically pure chloromethyl menthyl ether (6) with the anion of 5 provides the menthyloxymethyl complex 7. Photolysis of 7 in the presence of triphenylphosphane induces migratory insertion of carbon monoxide to provide a racemic mixture of the diastereomeric phosphane-substituted menthyloxymethyl complexes (-)-(/ )-8 and ( + )-( )-8 which are resolved by fractional crystallization. Treatment of either diastereomer (—)-(/J)-8 or ( I )-(.V)-8 with gaseous hydrogen chloride (see also Houben-Weyl, Vol 13/9a, p437) affords the enantiomeric chloromethyl complexes (-)-(R)-9 or (+ )-(S)-9 without epimerization of the iron center. 

There are some problems associated with the use of functional derivatives of carboxylic acids. Long-chain acid anhydrides are not commercially available, and one half of the acylation reagent is not utilized. Acyl chlorides require the use of tertiary base catalysts, whose double role has been explained before. Some of the intermediate acyl ammonium compounds formed are, however, insoluble in the solvent system. Examples include RCO - N+EtsCL in LiCl/DMAc, where RCO refers to the propionyl, hexanoyl, and stearoyl moiety, respectively. Hexanoyl- and stearoyl-pyridinium chlorides are also insoluble in the same solvent system [185]. 

The sulfonylated and acylated PPO presents solubility characteristics which are completely different from those of the parent PPO. Table V presents the solubility of some modified structures compared to those of unmodified PPO. It is very important to note that, after sulfonylation, most of the polymers become soluble in dipolar aprotic solvents like dimethyl sulfoxide (DMSO), N,N— dimethylformamide (DMF) and N,N-dimethylacetamide (DMAC). At the same time it is interesting to mention that, while PPO crystallizes from methylene chloride solution, all the sulfonylated polymers do not crystallize and form indefinitely stable solutions in methylene chloride. Only some of the acetylated polymers become soluble in DMF and DMAC, and none are soluble in DMSO. The polymers acetylated with aliphatic acid chlorides such as propionyl chloride are also soluble in acetone. 

Lack of selectivity in the reaction of the /3-D-glucoside derivative with one molar equivalent of benzylthiocarbonyl chloride has also been noted 40% of the 2,3-diester and 40% of the starting material were isolated.40 Similarly, unimolar benzoylation of phenyl 4,6-0-benzylidene-/3-D-glucopyranoside gave only 9% of the 3-ester, together with 47% of the 2,3-diester.41 Acylation of benzyl 4,6-0-benzylidene-/8-D-glucopyranoside with acetic anhydride-pyridine-pyridine hydrochloride yielded,42 in contrast to the reaction with the... 

The acyl anion chemistry of acylzirconocene chlorides has also been applied to the stereoselective preparation of ( )-a,(3-unsaturated selenoesters and telluroesters (Scheme 5.35) [38]. Although no carbon—carbon bond was formed, this reaction reflects the synthetic interest in ( )-a,(3-unsaturated selenoesters and telluroesters, which are well-known precursors of acyl radicals and acyl anions, respectively. 

It must further be mentioned that the acylation of alcohols, phenols, and amines with acid chlorides (and also anhydrides) is now frequently carried out in pyridine solution instead of according to the older Schotten-Baumann method (action of acid chloride in aqueous-alkaline suspension). The hydrogen chloride is fixed by the pyridine. 

The carbonyl group of an acid chloride is also a sufficiently electropositive center that acylation of a sulfinate ion occurs at oxygen (123) rather than sulfur (Schank, 1967 Kobayashi, 1966b). The mixed sulfinic-carboxylic anhydrides... 

A method of directly acylating 6-APA with phenylglycine chloride hydrochloride also has been proposed [37]. 

Acylation of ester enolates can also be carried out with more reactive acylating agents such as acid anhydrides and acyl chlorides. These reactions must be done in inert solvents to avoid solvolysis of the acylating agent. The preparation of diethyl benzoylmalonate (entry 1 in Scheme 2.14) is an example employing an acid anhydride. Entries 2-5 illustrate the use of acyl chlorides. Acylations with these more reactive compounds can be complicated by competing O-acylation. /V-Mcthoxy-iV-methylamidcs are also useful for acylation of ester enolates. 

Procedures for synthesis of ketones based on coupling of organostannanes with acyl chlorides have also been developed.152 153 The catalytic cycle is similar to that involved in the coupling with alkyl or aryl halides. The scope of compounds to which the procedure can be applied is wide and includes successful results with tetra-n-buty lstannanc. This example implies that the reductive elimination step in the mechanism can compete successfully with -elimination. 

Sulfurous oxychloride is used as a chlorinating agent for making sulfoxides and acyl chlorides. It also is used in pesticide formulations and to prepare anhydrous metal halides from their hydrated halides or hydroxides. 

Polyamides derived from o-glucose and o-glucosamine by interfacial and solution polycondensations of the sugar diamino derivatives with aromatic and aliphatic acyl chlorides have also been described [83]. 

The scope of the Negishi-coupling is not limited to aryl and vinyl halides and sometimes acyl chlorides might also be converted to ketones by this protocol. The 2,3-dihalopyrrole derivative shown in 6.22. was converted into its 2-lithio derivative by selective lithium-halogen exchange at -78 °C. Addition of zinc chloride effected the formation of the appropriate pyrrolylzinc chloride, which was coupled with a functionalised butyroyl chloride in the presence of tetrakis(triphenylphosphino)palladium and furnished the expected 2-acylpyrrole in 61% yield.27... 

TV-Acylation of (73) can be achieved with acyl chlorides and pyridine or triethylamine, or with ketene (75S547 p. 560). 7V-Trimethylsilylazetidin-2-ones have been reported to undergo acyldesilylation on treatment with acetyl chloride. Acylation of (73) with imidates (78) at 150-160 °C was followed by ring expansion to give the pyrimidin-4-ones (79). Pyrimid-4-ones were obtained from a similar reaction of imidates with 4-alkoxyazetidin-2-ones (74CB270). Acylation with subsequent ring expansion also occurs with dithioimidates (73CPB1305). 

Recently, it has been shown that acyl chlorides may be prepared from cyanuric chloride and carboxylic acids (79TL3037). Cyanuric chloride is also valuable for effecting the formation of macrocyclic lactones (Scheme 44) (80TL1893). Similarly, aryl oximes may be converted to... 

Acyl chlorides. Acyl chlorides are formed rapidly by reaction of carboxylic acids with SOCl2 and pyridine in CH2C12 at 25°. The dicyclohexylammonium salts of carboxylic acids react particularly rapidly (ca. 1 minute). The acid chlorides prepared in situ in this way react with amines in the presence of DMAP or DBU to form amides in >85% yield. This SOCl2-Py method is also useful for peptide synthesis with slight racemization. 

Acyl chlorides were also tested in acylations promoted by B(OTf)3.231 Acylation of benzene and toluene in competitive reactions (molar ratio = 5 1) with acetyl chloride shows high para selectivity (92-95% with 2.5-7% of meta, kT/kB — 31-73), whereas the para isomer is formed only with 72-75% selectivity (8-10% of meta, k lkK = 78) in benzoylation with benzoyl chloride. Acetylation appears not to be affected by significant isomerization as indicated by isomer distributions and relative reactivity data. 

The mechanism of the Friedel-Crafts acylation reaction, formulated below for reactions using acid chlorides, probably involves the acylium ion (2) as the reactive electrophilic species, although an electrophilic complex (1) between the acid chloride and aluminium chloride may also be involved. 

Ullmann synthesis, ] 15 Unsaturated acid chlorides, acylation, 49 Uranium derivatives, 154 Uranyl ions, 108 Urea, with azothiazoles. 111 to thiazolyl urea, 56 see also Thiazolyl urea Urine, 2-aminothiazoles in, 85 metabolite in, 85... 

Acyl chlorides may also be condensed with various benzene-1,2-dithiols. For example substituted benzene-1,2-dithiols (276) react with acyl chlorides in the presence of perchloric... 

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