Acylation isocyanides

ORGANOMETALLIC COMPLEXES OF ISOMERIC ACYL ISOCYANIDES CHROMIUM CARBONYL (ACYL ISOCYANIDE) AND (ACYL CYANIDE) COMPLEXES... 

The quite labile acyl isocyanides on the other hand may be obtained from acyl iodides with AgCN in CH2CI2 similarly imidoyl bromides give rise to imidoyl isocyanides (Scheme 25). Both types of compounds decompose quite easily under comparatively mild conditions. Acyloxy isocyanides are well known too. ... 

N-Acyl isocyanides. These unstable compounds can be prepared readily by treatment of carboxylic acid iodides with silver cyanide in CH2CI2 at 20°. N-Benzoyl isocyanide was formed in this way in 73% yield. 

Relative susceptibility of isocyanide and carbonyl ligands to insertion depends on reaction systems. The greater thermodynamic stability of the iminoacyl complexes than the acyl complexes was demonstrated by thermal isomerization of acyl(isocyanide)molybdenum to iminoacyl(carbonyl)molybdenum complexes (Eq. 7.13) [94]. 

Ohba and co-workers developed a general synthesis of chiral iV-protected 5-(aminomethyl)oxazoles from a-lithiated isocyanides and Af-protected amino acid esters (Scheme 1.101). Metalation of an alkyl or benzyl isocyanide with n-BuLi or LDA and acylation with an A-Boc-ot-amino acid methyl ester afforded an iV-Boc-a-amino acid acyl isocyanide 369, which cyclized to a chiral A-Boc-5-(aminomethyl) oxazole 370. The products were obtained in > 98% ee based on chiral HPLC analysis. The yields of 370 were somewhat variable, ranging from 45 to 91%. A-Boc-protected glycine, alanine, phenylalanine, proline, serine, and (9-benzyl serine were all compatible with these reaction conditions. 

Imidoyl isocyanides PhN=C(R)NC, formed by the action of silver cyanide on imidoyl bromides in chloroform, differ from the structurally related and better known iV-acyl isocyanides in that, on heating, they undergo isomerization to the thermodynamically more stable isomeric imidoyl cyanides ArN=C(Ph)CN rather than trimerization/ Also formed, in minor amount (10—30%), is 2,2 -diphenyl-4,4 -bisquinazoline (220), probably via head-to-tail dimerization of the isocyanide followed by a double electrocyclic ring-closure of the extended TT-system (219). Attempts to transform /3-styryl isocyanides into 2,2 -... 

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