Vinyl isocyanides

Mixed phosphine isocyanide complexes [Co(CNR)3phos2] and [Co-(CNR)4diphos], (the former were alluded to earlier (ref. 90, p. 185)), are reported to be obtained from Co(phos)2Cl2 and isocyanides (50). A vinyl isocyanide complex [Co(CNC2H3)5] is reported (94). 

D. Miscellaneous.—The base-catalysed addition of diphenylphosphine to excess vinyl isocyanide gave (22). However, the reaction of phenyl-... 

Aldehydes and the corresponding 2-aminopyridine, pyrazine, or pyrimidine are admixed in presence of a catalytic amount of clay (50 mg) to generate iminium intermediate. Isocyanides are subsequently added to the same container and the reactants are further exposed to MW to afford the corresponding imidazo[l,2-a]pyridines, imi-dazo[l,2-a]pyrazines and imidazo[l,2-a]pyrimidines (Scheme 6.48). The process is general for all the three components, e. g. aldehydes (aliphatic, aromatic and vinylic), isocyanides (aliphatic, aromatic and cyclic) and amines (2-aminopyridine, 2-amino-pyrazine and 2-aminopyrimidine). A library of imidazo[l,2-a]pyridines, imidazo[l,2-ajpyrazines and imidazo[l,2-a]pyrimidines can be readily obtained by varying the three components [151]. 

Vinyl isocyanide, 1106 Zinc cyanide, 1000 ACETYLENIC COMPOUNDS ALKYLMETALS ALKYNES... 

Benzyl isocyanide is a useful precursor of compounds containing the ot-benzylamino moiety. Substituted styrenes, vinyl isocyanides, 2-oxa-zolines, 1-pyrrolines, imidazoles, and a-amino acids and ketones can be obtained by metalation of isocyanides with butyllithium12 or copper salts,13 and subsequent reaction with various electrophiles.12... 

Carbon-transition metal bonds can also be formed by cocondensing transition-metal atoms with isonitriles. Thus, using Ni and Fe with t-butyl isocyanide, methyl isocyanide, cyclohexyl isocyanide and vinyl isocyanide the NiL4 and FeL, complexes are formed. Palladium cocondensed with isonitriles yields PdLj polymeric structures with terminal and bridged isonitrile ligands ... 

Vinyl isocyanides. Reaction of the lithium salt of (1) with carbonyl compounds gives vinyl isocyanides in 70-85 % yield ... 

AT-Vinyl-substituted isocyanides 57 have been polymerized in the presence of nickel catalysts, yielding poly(vinyl isocyanide)s [79]. The solubility and stability of these polymers very much depends upon the substituent on the vinyl group. Substituted vinyl isocyanide, (CH3)2C=CHNC, afforded polymers that were soluble in chloroform when freshly prepared, although they became insoluble on standing for several days, even at temperatures of -10 °C. The polymerization of vinyl isocyanide proceeded in hydrocarbon solvents, unlike aryl or alkyl isocyanides, which required an alcoholic solvent for efficient polymerization. 

Reactions.—Nucleophilic Attack on Carbon. Activated olefins and acetylenes. The full paper describing addition of P—H bonds to vinyl isocyanides has been published. The reaction of diphenylphosphine with vinyl isocyanide in the presence of base proceeds normally, whereas the corresponding reaction with phenylphosphine gave the 1,3-azaphosphole (24). 

Phenylphosphine refluxed with excess vinyl isocyanide in tetrahydrofuran in the presence of ca. 15% K-rer -butoxide 4,5-dihydro-3-phenyM,3-azaphosphole. Y ca. 90. F. reactions of vinyl isocyanide with group V element(lll) compds. s. R. B. King and A. Efraty, Am. Soc. 93, 564 (1971). 

Unsaturated isocyanides, too, have been the focus of considerable attention. Vinyl isocyanides have been prepared either by Cu20-catalysed isomerisation of allylic analogues or by the Schollkopf method of reacting aldehydes with situ metallated methyl isocyanide followed by dehydration of the adducts.The... 

Various vinyl isocyanides 1521-1525 are prepared from oximes (for example, 1519) by reductive formylation and dehydration of the resulting vinyl formamides (for example, 1520) with phosgene in 40-97% yield [1167]. For the dehydration step, DABCO proved to be the most effective base among acid scavengers (EtsN, pyridine, and quinoline were also used). 

Cyclohexen-l-yl isocyanide 1521, rac-4-fert-butyl-cyclohexen-l-yl isocyanide, and rac-4-phenyl-cyclohexen-l-yl isocyanide were likewise prepared by a similar method using gaseous phosgene to furnish the vinyl isocyanides in yields of 71-80% [1168], These were applied in a multicomponent approach to novel totally protected precursors of PNA monomers through an Ugi 4CR. 

General procedure. Vinyl isocyanides [1168] The appropriate formamide (0.2 mol) and abs. triethylamine (64 mL) were dissolved in dichloromethane (500 mL). The solution was cooled to 0 °C and phosgene (20 g, 0.202 mol) was introduced over a period of about 2 min. After stirring for 1 h at 0 °C, water (140 mL) was added and the layers were separated. The organic layer was washed with water (2 x 140 mL) and dried over MgS04. After evaporation of the solvent in vacuo, the residue was subjected to flash chromatography on silica gel to furnish 1521 in 71% yield. 

A communication from Baldwin on triflic anhydride (trifluoromethanesulfonic anhydride) describes this reagent as being superior for the conversion of form-amides and vinyl formamides to isocyanides and vinyl isocyanides in yields of about 80% [1237]. Dehydration with triflic anhydride seems to be the method of choice for preparing epoxy isocyanides (see below). 

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