Oxalyl chloride isocyanates

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). 

Commercially important arenesulfonyl isocyanates are not directly accessible from the corresponding sulfonamides via phosgenation due to lack of reactivity or by-product formation at elevated temperatures. A convenient method for their preparation consists of the reaction of alkyl isocyanates with sulfonamides to produce mixed ureas which, upon phosgenation, yield a mixture of alkyl and arenesulfonyl isocyanates. The desired product can be obtained by simple distillation (16). Optionally, the oxalyl chloride route has been employed for the synthesis of arenesulfonyl isocyanate (87). 

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. ° ... 

Diesters of phosphoramidic acid are converted to the corresponding isocyanates by phosgene but with A-substituted derivatives the phosphoramidic chlorides are formed. In a similar reaction oxalyl chloride... 

Chlorine, positive , iodometric determination of, 48, 5 reaction with 2-butyne, 46, 34 a-Chloroacetamide, reaction with oxalyl chloride to give a-chloroacetyl isocyanate, 46, 16... 

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

Japanese workers prepared examples of 2-alkenyl-4,5-oxazolediones 40a and 40b, which are key intermediates in the synthesis of alkenoyl isocyanates 41a and 41b (Scheme 6.13). These reactive monomers are precursors to a variety of functionalized polymers including instantaneously curable compositions. Thus, reaction of oxalyl chloride with acrylamide 39a or methacrylamide 39b affords 40a and 40b isolated as hydrochloride salts in high yields. Subsequent decomposition of the 2-alkenyl-4,5-oxazolediones in the presence of a metal halide or synthetic zeolite affords 41a and 41b contaminated with varying amounts of 42a and 42b. The synthesis and reactions of other 2-substituted 4,5-oxazolediones have been described independently by Speziale and co-workers ° and Sasaki and co-workers. ... 

Imines from a-halo carbonyls treated with oxalyl chloride are reported to give a-halo isocyanates, which upon careful hydrolysis cyclize to l,3-oxazetidin-2-ones. However, it is difficult to tell how general such a procedure might be since decarboxylation could compete with cyclization (Scheme 69) (80S571). 

On the pages which follow, general methods are illustrated for the synthesis of a wide variety of classes of organic compounds including acyl isocyanates (from amides and oxalyl chloride p. 16), epoxides (from reductive coupling of aromatic aldehydes by hexamethylphosphorous triamide p. 31), a-fluoro acids (from 1-alkenes p. 37), 0-lactams (from olefins and chlorosulfonyl isocyanate p. 51), 1 y3,5-triketones (from dianions of 1,3-diketones and esters p. 57), sulfinate esters (from disulfides, alcohols, and lead tetraacetate p. 62), carboxylic acids (from carbonylation of alcohols or olefins via carbonium-ion intermediates p. 72), sulfoxides (from sulfides and sodium periodate p. 78), carbazoles... 

Oxazolidinediones have been prepared by one-pot condensation of benzyl cyanides, isocyanates, and 2-chloro-2-oxoacetate as shown in Scheme 85. The anion derived from BuLi deprotonation of benzyl cyanide attacks the isocyanate to give intermediates 306, which can undergo condensation and cyclization with ethyl oxalyl chloride to give the 4,5-oxazolidinedione products <2004SL1963>. 

The isocyanate can be generated in situ by the reaction of an amine and oxalyl chloride, and subsequent reaction with HCl and then an alcohol gives the carbamate. Polyurethanes are made by combining compounds with two NCO groups with... 

The demonstrated utility of these high-reactive isocyanates prompted us to search for a phosgenation process more economical than the oxalyl chloride route. Our attempts succeeded in the development at a laboratory scale of a method based on the reaction of phosgene with N,N-disilyl amides as depicted in scheme 161 (Ref. 215). 

It is well known that oxalyl chloride reacts with non-substituted amides to afford acyl isocyanates in high yields (Ref. 214). In contrast, phosgene acts as a dehydrating agent to give nitriles as shown in scheme 160. This interesting reaction, its mechanism and applications will be discussed in volume 2. 

On the pages which follow, general methods are illustrated for the synthesis of a wide variety of classes of organic compounds including acyl isocyanates (from amides and oxalyl chloride p. 16), epoxides (from reductive coupling of aromatic aldehydes by hexamethylphosphorous triamide p. 31), a-fluoro acids (from... 

Finally, acyl isocyanates have been prepared from carboxamides by use of oxalyl chloride in place of phosgene.636... 

Preparation of Acyl Isocyanates and Aryl Isocyanates. Certain primary carboxamides can be converted to acyl isocyanates in yields from 36-97% with the reagent (eq 22) Phosgene gives nitriles under similar conditions. Oxalyl chloride has found limited application for the preparation of triazine and quinone isocyanates. ... 

The reaction of thionyl chloride with 1,3-disubstituted ureas affords either N-sulfinylamines and isocyanates (R = n-alkyl), or chloroformamidine hydrochlorides (R = sec-alkyl, t-alkyl) However, the reaction of oxalyl chloride with ureas does not produce chloroformamidines, parabanic acids being the sole reaction product (51.6 5,66 ... 

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