Acyl chlorides oxalyl chloride

This method is usually used for producing small amounts of valuable acyl chlorides—oxalyl chloride is much more expensive than thionyl chloride. DMF... 

Y-carboxylic acid (74) by approaches involving either acyl chlorides (oxalyl chloride route) or mixed carbonic anhydrides (isobutyl chloroformate route) (Scheme 120). An alternative route to (73) involves selective attack at the Y-carbonyl of anhydride (71) with diazomethane however the DON precursor (72) could not be prepared using this method. 

Indolo[3,2-3]carbazoles bearing a carbonyl substituent at the 6-position have been synthesized directly by an intramolecular cyclization approach from dichloroacetyl substituted precursors <2004EJO2593>. However, due to a facile decarbonylation under the reaction conditions it was found to be more expedient to employ esters, such as 165, produced by acylation with oxalyl chloride (Equation (79) Table 4). 

An interesting approach involving functionalization of each of the six unsubstituted positions of 6-methylindole (96) was followed in the third synthesis of 7-methoxymitosene [35]. This route required a relatively high number of steps, 17, and the overall yield was 3%. As outlined in Scheme 13, 96 was substituted on nitrogen by a 3-chloropropyl group and then a carbomethoxy group was introduced by acylation with oxalyl chloride, decarbonylation at 120 °C, and treatment with methanol. The product (97) was acylated at C-5 by... 

On the way to l,2-di(thien-3-yl)imidazol(Mies 48, 2,5-dimethylthiophene was acylated with oxalyl chloride, giving diketcme 47 in 35% yield (Scheme 50) [64,68],... 

Certain activated carbon atoms may be conveniently acylated with oxalyl chloride to afford an intermediate which is readily decar-boxylated to afford a carboxylic acid. 

Preparation of Arylcarboxylic Acids and Derivatives. The general Friedel-Crafts acylation principle can be successfully appHed to the preparation of aromatic carboxyUc acids. Carbonyl haUdes (phosgene, carbonyl chloride fluoride, or carbonyl fluoride) [353-50-4] are diacyl haUdes of carbonic acid. Phosgene [75-44-5] or oxalyl chloride [79-37-8] react with aromatic hydrocarbons to give aroyl chlorides that yield acids on hydrolysis (133) ... 

Acylation. Acylation is the most rehable means of introducing a 3-substituent on the indole ring. Because 3-acyl substituents can be easily reduced to 3-aLkyl groups, a two-step acylation—reduction sequence is often an attractive alternative to direct 3-aLkylation. Several kinds of conditions have been employed for acylation. Very reactive acyl haUdes, such as oxalyl chloride, can effect substitution directiy without any catalyst. Normal acid chlorides are usually allowed to react with the magnesium (15) or 2inc (16) salts. The Vilsmeier-Haack conditions involving an amide and phosphoms oxychloride, in which a chloroiminium ion is the active electrophile, frequentiy give excellent yields of 3-acylindoles. 

Specialty Isocyanates. Acyl isocyanates, extensively used in synthetic appHcations, caimot be direcdy synthesized from amides and phosgene. Reactions of acid haUdes with cyanates have been suggested. However, the dominant commercial process utilizes the reaction of carboxamides with oxalyl chloride [79-37-8]. CycHc intermediates have been observed in these reactions which generally give a high yield of the desired products (86). 

A more practical solution to this problem was reported by Larson, in which the amide substrate 20 was treated with oxalyl chloride to afford a 2-chlorooxazolidine-4,5-dione 23. Reaction of this substrate with FeCL affords a reactive A-acyl iminium ion intermediate 24, which undergoes an intramolecular electrophilic aromatic substitution reaction to provide 25. Deprotection of 25 with acidic methanol affords the desired dihydroisoquinoline products 22. This strategy avoids the problematic nitrilium ion intermediate, and provides generally good yields of 3-aryl dihydroisoquinolines. 

When the substrate is oxalyl chloride (ClCOCOCl) and the reagent an unsubstituted amide, an acyl isocyanate (RCONCO) is formed. The normal product (RCONH-COCOCl) does not form, or if it does, it rapidly loses CO and HC1. ° ... 

Treatment of N-benzoyl-L-alanine with oxalyl chloride, followed by methanolic triethylamine, yields methyl 4-methyl-2-phenyloxazole-5-carboxylate 32 <95CC2335>. a-Keto imidoyl chlorides, obtained from acyl chlorides and ethyl isocyanoacetate, cyclise to 5-ethoxyoxazoles by the action of triethylamine (e.g.. Scheme 8) <96SC1149>. The azetidinone 33 is converted into the oxazole 34 when heated with sodium azide and titanium chloride in acetonitrile <95JHC1409>. Another unusual reaction is the cyclisation of compound 35 to the oxazole 36 on sequential treatment with trifluoroacetic anhydride and methanol <95JFC(75)221>. 

N-Silylated peptide esters are acylated by the acid chloride of N-Cbo-glycine to N-acylated peptide bonds [11]. Likewise, acid chlorides, prepared by treatment of carboxylic acids with oxalyl chloride, react with HMDS 2 at 24°C in CH2CI2 to give Me3SiCl 14 and primary amides in 50-92% yield [12]. Free amino acids such as L-phenylalanine or /5-alanine are silylated by Me2SiCl2 48 in pyridine to 0,N-protected and activated cyclic intermediates, which are not isolated but reacted in situ with three equivalents of benzylamine to give, after 16 h and subsequent chro-... 

The traditional method for transforming carboxylic acids into reactive acylating agents capable of converting alcohols to esters or amines to amides is by formation of the acyl chloride. Molecules devoid of acid-sensitive functional groups can be converted to acyl chlorides with thionyl chloride or phosphorus pentachloride. When milder conditions are necessary, the reaction of the acid or its sodium salt with oxalyl chloride provides the acyl chloride. When a salt is used, the reaction solution remains essentially neutral. 

Methyl 3-acyl-l-diphenylmethyleneamino-4,5-dioxo-4,5-dihydro-l//-pyrrole-2-carboxylates 489 are formed from 488 and oxalyl chloride in good yields. Preparative thermolysis of these compounds at 130-140°C gives mixtures of dipyrazolo[l,2- l,2- [l,2,4,5]tetrazines 491 as major products and pyrazoles 492 as minor hydrolytic by-products. The intermediacy of mesoionic compound 490 is expected (Scheme 83) <2004T5319>. 

A differently fused pyrrolopyridopyrazine is obtained from 2,3-diaminopyridine, an acylpyruvic acid, and oxalyl chloride (Scheme 59) <2000CHE1114> and imidazopyridopyrazines such as 250 have been prepared by acylation of o-aminohalogenopyridines with carbonylimidazole dimer (Equation 74) <2001TL4297>. 

When alkyl oxalyl chlorides were employed instead of acyl halides, symmetrical dibenzyl ketones were formed in good yields(44). Transition metal carbonyls or metal salts/carbon monoxide have generally been used for... 

Acyl hydrazides are useful precursors for the synthesis of 1,2,4-triazoles. Reaction of acyl hydrazides 149 with imidoylbenzotriazoles 148 in the presence of catalytic amounts of acetic acid under microwave irradiation afforded 3,4,5-trisubstituted triazoles 150 <06JOC9051>. Treatment of A-substituted acetamides with oxalyl chloride generated imidoyl chlorides, which reacted readily with aryl hydrazides to give 3-aryl-5-methyl-4-substituted[ 1,2,4]triazoles <06SC2217>. 5-Methyl triazoles could be further functionalized through a-lithiation and subsequent reaction with electrophiles. ( )-A -(Ethoxymethylene)hydrazinecarboxylic acid methyl ester 152 was applied to the one-pot synthesis of 4-substituted-2,4-dihydro-3//-1,2,4-triazolin-3-ones 153 from readily available primary alkyl and aryl amines 151 <06TL6743>. An efficient synthesis of substituted 1,2,4-triazoles involved condensation of benzoylhydrazides with thioamides under microwave irradiation <06JCR293>. 

Acyl chlorides are converted in good yield into symmetrical carboxylic acid anhydrides upon treatment with dilute aqueous sodium hydroxide at -I0°C in the presence of a tetra- -butylammonium salt [76, 77]. Yields are considerably lower when Aliquat is used. In a similar manner, chloroformates and ethyl oxalyl chloride are converted into carbonic hemi-ester anhydrides. 

The carboxylic functionalities inserted onto the tubes can be used as platforms to obtain further transformations (Fig. 3.5). A commonly utilized route is the reaction of carboxylic groups with thionyl chloride or oxalyl chloride to prepare the corresponding acyl chlorides, which are useful intermediates for amidation or esterification reactions. Amides can also be prepared directly from the acids by means of standard solution chemistry conditions, using carbodiimide derivatives in the presence of the selected amine. 

There are several chemical reactions that can be used as an alternative to achieve covalent functionalization of CNTs. Two of them are amidation and/or esterification reactions. Both reactions take advantage of the carboxylic groups sitting on the side-walls and tips of CNTs. In particular, they are converted to acyl chloride groups (-C0-C1) via a reaction with thionyl (SO) or oxalyl chloride before adding an alcohol or an amine. This procedure is very versatile and allows the functionalization of CNTs with different entities such as biomolecules [154-156], polymers [157], and organic compounds [158,159] among others. 

Isocyanates, acyl, derivatives of, 46, 17 preparation using oxalyl chloride, 46,17... 

Syntheses of a series of pyrrolo-benzazepine acetic acids 381 have been reported (Scheme 77 (1994MI385)). They include acylation of the core heterocycle with ethoxy oxalyl chloride in the first step to afford ketoesters 380. This sequence can also be successfully applied to a pyrrolo-benzothiazepine ring system. 

The formation of an acyl halide involves the reaction of a carboxylic acid with a halogen source. The common halogen sources tire compounds like PX3, PXj, ClOCCOCl (oxalyl chloride), or SO.V2> where. Y is a halogen. The most commonly used acyl halides are the chlorides, and the simplistic reaction is RCOOH —> RCOCl. Figure 12-15 illustrates the mechanism using thionyl... 

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