Acylcyanides

AB-Dinorsteroids have been prepared by Dauben et al from B-nor-A" -3-ketones by reactions analogous to the sequence (4) - (7). Pyrolysis of the B-nor-2,3-seco diacid anhydride gives the AB-dinor-A -2-ketone in 5 % yield. However, refluxing the diacid with acetic anhydride containing potassium cyanide for 2 days gives the ketone in 50-60% yield, apparently by base-catalyzed cyclization of an intermediate bis-acylcyanide. 

Ho and coworkers" have observed that the addition of small amounts of solid KCN (0.2 equivalents) can effectively accelerate the formation of hydroxamic acids 112 from methyl esters 111 (Scheme 58). The authors suggested that this reaction proceeds through an acylcyanide intermediate followed by nucleophilic substitution by 50% aqueous hydroxylamine at room temperature. The use and advantage of this methodology have been demonstrated for both solution-phase and solid-phase applications. 

Nonactivated nitriles undergo cycloaddition with especially reactive nitrile oxides (e.g., trifluoro-acetonitrile oxide <84JOC919> or bromocyanogen oxide <89JHC23>, acylcyanide oxides <87JHC697>, or cyanogen monooxide (Equation (31)) <91IZV1916>. 

Reaction of acylcyanides (485) with amidrazones (453), semicarbazide (459a), thiosemicarbazide (459b) or aminoguanidine (460a) is used for the synthesis of 5-amino-... 

Acylcyanides. The oxidation of cyan cyanides is catalyzed by (PPhsljRuCI.-. Th acylation of amino alcohols and polyaminci Carbonylation. A new route to 2i5//> lation of allylic alcohols. ... 

Acylcyanides. The oxidation of cyanohydrins with t-BuOOH to furnish acyl-cyanides is catalyzed by (PPhj),RuCl2. The products can be used for selective N-acylation of amino alcohols and polyamines. 

The reactions of acylcyanides with amidrazones 209, semicarbazides, thiosemicarbazides 218, and aminoguanidines 228 result in the formation of 5-amino-l,2,4-triazines <2004SOS(17)357>, 5-amino-l, 2,4-triazin-3-ones, the corresponding 3-thiones, and 3,5-diamino-l,2,4-triazines <2003TL5657, 2004SOS(17)357> (Scheme 143). 

Subst. carboxylic acid amides from acylcyanides... 

N-Acylcarboxylic acid amides s. a. Diacylamines, mixed Acyl compounds, active s. Carboxylic acid esters, active Acylcyanides... 

Further addition, however, can occur, and the a,a-dicyanoalkoxide can be trapped by an acyl chloride. Such a procedure was used in the preparation of a precursor of tetracyanoquinodimethane.75 The cyanide anion adds more efficiently to the bis-acylcyanide under sonication than in the presence of lS-c-6. 

The reduction of acylcyanide using neat (f )-Alpine-Borane affords the corresponding (i )-P-amino alcohols [4cj. The reduction of acylcyanide and subsequent workup is not a straightforward process. The reaction of benzoylcyanide with neat Alpine-Borane (1.5 equiv) is complete within 2 h. The cyanohydrin-9-BBN adduct builds up to maximum, and then decreases with the appearance of a 9-BBN-benzyl alcohol adduct. Apparently, the 9-BBN-cyanohydrin adduct undergoes an elimination reaction to give benzaldehyde, which then undergoes reduction. The results indicate that the desired bimolecular reduction process can compete with the elimination reaction. 

The clean reduction, however, is achieved [4c] using 15 mmol of neat solution of (i )-Alpine-Borane and acylcyanide (10 mmol). The progress of the reaction is monitored by ff NMR (appearance of a-pinene signal at 5.2 ppm). The reaction mixture is then treated with methanol containing cobaltous chloride [21], followed by the addition of sodium borohydride (Eq. 26.12) [4c]. 

Table 26.13 Yields and Borane (from 92% ee (+) ee of substituted 2-ethanolamine from acylcyanides using neat Alpine--a-pinene) [4c] ...

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