Isocyanato-chloroformate

The reactions of amino acids or amino alcohols with phosgene are interesting since they provide in one step molecules with two different functional groups, namely isocyanato acid chlorides or isocyanato chloroformates. 

A procedure using trichloromethyl chloroformate (diphosgene) has been successfully applied in the synthesis of isocyanato acid chlorides and isocyanato chloroformates from amino acids and amino alcohols, respectively [161,1016]. 

All of the synthesized compounds described thus far in this chapter have been of monovalent reactivity, i.e. the compounds consist of one or more active functional groups of the same selectivity and, where appropriate, one or more further non-active functions. Difunctional compounds such as isocyanato-chloroformate 108 [60] (Section 4.2.1), 446 [300] (Section 4.3.1.4), isocyanato-carbamoyl chloride 179 [111, 112] (Section 4.2.2.2), isocyanato acid chloride 1231 [447] (Section 4.3.5.4), and 1343 [1016] (Section 4.4.2.3), also fall into this category because all of their functions are of the same selectivity, in these examples electrophiles. 

Iron tricarbonyl dieme complex, 57, 16 Isobutyl chloroform.ate, 59, 165 Isobutylene, 59, 164 Isobutyl fluoride, 5, 73 Isobutyryl chloride, 59, 29 Isocyanato acid chlotrides, from amino acids, 59, 200... 

Trichloromethyl chloroformate has proven effective in the preparation of N-carboxy-a-amino acid anhydrides from amino acids, and various compounds having isocyanate, acid chloride, and chloroformate groups.For example, trichloromethyl chloroformate may be used instead of phosgene in the preparation of 2-tert-butoxycarbonyloxyimino-2-phenylacetonitrile. The use of this reagent is illustrated here by the synthesis of 3-isocyanato-propanoyl chloride from 3-aminopropanoic acid hydrochloride. 

The formation of the a,a>-isocyanato alcohols has been confirmed by IR and H NMR spectroscopy. In the IR spectrum of a solution of the product in chloroform, a strong absorption due to the N=C=0 stretch is seen at 2274 cm . H NMR spectra show the absence of any side products and also prove the relative stability of a,co-isocyanato alcohols in solution however, concentration to dryness furnished undefined products. 

Benzyl chloroformate and carbon disulfide (CS2) have been used to prepare Cj-Q aliphatic isocyanates 399, e.g. l-isocyanato-2-methyl-propane, 4-isocyanato-octane, 1-... 

Methyl 2-isocyanato-4-methylpentanoate added to benzyl 3-methylcarbazate hydrochloride and triethylamine in chloroform, and allowed to stand 16 hrs. at 20-22° methyl N-benzyloxycarbonyl-a-azaalanyl-L-leucinate. Y 85%. F. e. s. A. S. Dutta and J. S. Morley, Soc. Perkin I 1975, 1712. 

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