Aryl isonitriles

Scheme 3.53. Synthesis of cyclopentaquinolines from aryl isonitriles and iodopentynes.

Aryl iodides, in Grignard reagent preparation, 9, 35 Aryl isocyanides, chalcogen—chalcogen additions, 10, 752 Aryl isonitriles, in insertion reactions, 1, 106-107 Aryl ketones, via intramolecular G—H functionalizations,... 

Insertion of isonitriles and carbenoids into the B-B and B-Si bonds have recently been developed as a method for synthesizing geminal bis(boryl) and boryl-silyl compounds (Scheme 24). The insertion of alkyl and aryl isonitriles into the B-Si bond proceeded at room temperature to provide monomeric (boryl)(silyl)imines 227.388,389 Alkylidene... 

Complete exchange of CO rarely occurs. However, reaction of Ni(CO>4 or CojfCO) with aryl isonitrile gives corresponding zero-valent complexes having only isonitrile ligands - ... 

The reactions of alkenyl carbene complexes with isonitriles can produce a variety of products whose distribution is sensitive to the nature of the isonitrile. Reacting 3 equiv. of aryl isonitrile with the alkenyl complex (383) produces the dihydro- y-carbolinone (385). 74 The ketenimine in (384) is liberated with a second equivalent of the isonitrile, and the the third equivalent undergoes a formal [4 -i- 2] cycloaddition with the free ketenimine. With sterically encumbered isonitriles, the ketenimine is more rapidly liberated from the metal by a second isonitrile and 2 equiv. are required to drive the reaction to completion. Free ketenimines that are generated in this manner can be trapped via their [4 + 2] cycloadditions with maleic anhydride. 7 Primary and secondary alkyl isonitriles will react with alkenyl carbene complexes to give cycloadducts that can be converted to pyrroles or products that contain five-member ring carbo-cycles. 7 ... 

Similar generation of palladium-silylene complexes may be involved in reaction of oligosilanes with aryl isonitriles giving four-membered rearranged products 95, although the mechanism has not yet been clarified (Eq.49) [81,86]. 

Aromatic isonitriles, particularly orf/jo-alkenyl-substituted aryl isonitriles, were also successfully employed by Fukuyama in the synthesis of indole derivatives [19]. Cyclization of compounds 26 was accomplished with tin radicals, and 6-membered ring closure did not significantly compete except in one case (R = -Bu) where, on the other hand, this problem was interestingly alleviated by using the Z-alkene instead of the Z-analog (Scheme 11). 

Very recently, a variant of this methodology was developed by the same author through tin-radical-mediated cyclization of ort/zo-alkenyl-substituted thioanilides [20], Moreover, Rainier et al. demonstrated that a very efficient synthesis of indoles can be carried out also with urz/to-alkynyl-substituted aryl isonitriles, provided that a TMS group is linked to the alkyne moiety [21] (Scheme 13). 

Although CO and alkenes are the most prominent substrates participating in migratory insertions, a variety of additional molecules are also susceptible to undergo such reactions. " " For example, both alkyl and aryl isonitriles (RNC) readily insert into M-C or M-H bonds to generate iminoacyl or formimidoyl derivatives, respectively... 

Recent progress in polymerization of isonitriles with organopalladium(II) complexes is shown below. Although reactions of aryl isonitriles with -ethynediyl-dipalladium(II) 6 and a related Pd-Pt heterodinuclear complex 7 at room temperature (r.t.) did not afford poly(isonitrile)s, selective double insertion of the isonitrile into the Pd—C bond (giving 8) or coordination of the isonitrile to the metal (giving 9) occurred (Scheme Polymer-... 

In the Pd-catalyzed polymerization of aryl isonitriles, the screw-sense of the helical structure was controlled by chiral groups introduced to the aryl moiety of the isoni-triles.f Thus, polymerization of (L)-menthyl ester of p- or m-isocyanobenzoic acid (13)... 

In a similar approach, quinolines 40 were prepared starting from alkoxyamine 36 and isonitriles 37 induced by TEMPO using an inter-intramolecular sequence [23] (Eq. 9.7). The precursor 36 via thermal C O homolysis and addition with aryl isonitrile 37 affords the corresponding imidoyl radical 38. Radical 38 can further react in a 5-ero-type cyclization to give the primary radical 39, which can undergo HAS and oxidation to provide the corresponding quinoline 40 ... 

To demonstrate the potential of these transformations, the synthesis of luotonin A (54, R=H) from 49 and aryl isonitrile 51 via a cascade radical annulation in the key step is presented (Scheme 9.6) [43b]. Radical addition of 50 onto 51 gave radical 52, which after 5-exo-dig cycUza-tion affords vinyl radical 53. This radical adds to arene to yield a cyclohexadienyl radical. Then, after oxidation, it delivers the pentacycUc alkaloid luotonin A (54, R = H). 

Electron-rich aryl isonitriles and 6-iodo-iV-propargylpyridones undergo a palladium-catalyzed cascade reaction at ambient temperature to afford llFf-indolizino[l,2-6]quinolin-9-ones in good... 

Alkyl and aryl isonitriles have strong absorptions in the regions 2175-2130cm (4.60-4.69pm) and 2150-2110cm (4,72-4.74pm) respectivelyThe intensity of the band is very sensitive to changes in the substituent. Isonitriles have a characteristic band, not found for nitriles, near 1595 cm (6.25 pm). 

A variety of new complexes has been described in which [CpM(CO)n] residues (M = Cr, Mo, and W) are attached to phosphorus, arsenic, sulphur, tin, and mercury ligands. The cyclic amino-phosphine PhP(OCH2CHg)aNH has been incorporated both as a mono- and bi-dentate ligand in [CpMo(CO)n] complexes. The diazenido complexes [CpM(CO)gN=NMe] (M = Mo and W) react with (THF)MX [M L = Cr(CO)5 and Mn(CO)gCp] to give thermally stable products of the type [CpM(CO)gN—N(Me)M Ln]. A free-radical mechanism has been proposed for reactions in which the CO ligands in [CpMo(CO)sI] are replaced by alkyl or aryl isonitriles these substitutions are catalysed by [CpMo(CO)s]g. 

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