Isocyanides, alkyl

The related mono-A/-alkylated carboranes, 7-(NH2R)-7-CB2qH22, can be prepared by treatment of decaborane(14) with alkyl isocyanides (125). 

One additional point should be discussed here, concerning the substantial emphasis that has been placed on the differences between alkyl and aryl isocyanides. It has been suggested, primarily on the basis of infrared evidence, that aryl isocyanides are better 7r-acceptors than alkyl isocyanides (90). Qualitatively this difference is easily rationalized. One can see that delocalization of charge into 7r -orbitals on an aryl ring in aryl isocyanide-metal complexes should be possible, whereas no such possibility exists for alkyl isQcyanide-metal complexes this means that aryl isocyanides should be better ir-acceptors. Of course, the simple qualitative model gives one no measure of the relative importance of this effect. 

Still, the ease of oxidation is obviously a property of considerable chemical importance. These differences require that the choice of aryl vs. alkyl isocyanides not be taken lightly. 

Detailed procedures for the synthesis of various often used [Ni°L4] complexes (L = phosphines, arsines, stibines, alkyl isocyanides) and [Ni°L 2] complexes (L = bipyridine, phenantroline, diphosphines, diarsines) have been compiled.2413... 

Imidazolines are also formed in silver cyanide-catalyzed cyclization of alkyl isocyanides with aliphatic diamines (Scheme 103).169 This simple synthesis can be applied in a general way with difunctional nucleophiles and has been used to prepare benzimidazoles, oxazoles, thiazoles, and oxazines.169 It is suggested that transient carbene complexes are formed in these reactions (cf. 87 in Scheme 103) but further work is required to ascertain the mechanism and scope of these processes. 

The scope of the silver cyanide-catalyzed reaction of difunctional nucleophiles with alkyl isocyanides has been described in the earlier section on imidazoles an example of the use of this simple approach in benzimidazole synthesis is illustrated in Scheme 105.169... 

Intermolecular bis-silylation of highly strained bicyclopropylidene with hexaorganodisilanes proceeds at 70 °C in the presence of the palladium// r/-alkyl isocyanide catalyst (Equation (34)).102... 

Addition of disilanes to isocyanides is catalyzed by palladium complexes, giving A-substituted bis(silyl)imino-methanes (Equation (53)).132 A wide range of isocyanides including aryl isocyanides and alkyl isocyanides can take part in the reaction. However, it is important to note that tert-alkyl isocyanides hardly undergo the bis-silylation reaction. This low reactivity of / r/-alkyl isocyanides allows their use as spectator ligands in the catalytic bis-silylations. 

Benzyne, which is generated in situ from 2-(trimethylsilyl)phenyl triflate and KF, acts as an alkyne congener in distannation in the presence of palladium-/ r/-alkyl isocyanide complex.157 A variety of substituted benzyne derivatives inserts into the Sn-Sn bond to give l,2-bis(stannyl)benzenes (Equation (59)). The reaction fails to occur in the presence of other palladium catalysts such as Pd(PPh3)4. 

The addition of the neutral silylborane to carbon-carbon triple bonds, in which both the boron and silicon groups were retained in the products, was achieved in 1996 by using palladium catalysts.217 Although, in the preliminary report, tert-alkyl isocyanide was used as the ligand on palladium, it was later reported that conventional phosphine... 

TEBA-Cl (50 mg, 0.2 mmol) is added to a well-stirred suspension of the alkyl isocyanide (10 mmol), the arylamine (10 mmol) and TosN(Cl)Na.3H20 (2.3 g, 10 mmol) in CH2C12 (50 ml) (CAUTION After an induction period, the reaction may become violent.) After 20 h, H20 is added and the organic phase is separated, dried (Na2S04), and evaporated to yield the N-tosylguanidine. 

Robertson, M.). and Angelid, R.J. (1994) Adsorption of aryl and alkyl isocyanides on powdered gold. Langmuir, 10,... 

Ontko, A.C. and Angelid, R.J. (1998) Effects of alkyl chain length on the adsorption of n-alkyl isocyanides (R-N=C) on gold powder. Langmuir, 14,1584—91. 

The addition of CF3CH2NC or CH2FCH2NC to [Ru(TPP)(CO)] yields [Ru(TPP)(CF3CH2NC)2] or [Ru(TPP)(CFCH2CH2NC)2] respectively. and F NMR spectroscopic data for these and the corresponding alkyl isocyanide derivatives suggest similarities in the bonding properties of members of this family of compounds. 

Arylsulfonyl methyl isocyanides (3) and isocyano esters (1) can also be prepared by the deprotonation of alkylisocyanides (5) by strong bases (nBuLi or NaH) followed by the addition of TosF and dialkyl carbonates or ethyl chloroformate, respectively (pathB) [37, 38]. However, the use of small and foul-smelling alkyl isocyanides makes this route less attractive. 

This compound reacts readily with alkyl isocyanides to give a cluster Pd(CNR)2 ,6 and with bulky alkyl phosphines to give two coordinated palladium(O) complexes.7... 

The metal-free eyclobutane-1,2-dioxime can be generated by oxidative displacement. It is interesting to note that, unlike ketene dimerization, head-to-head dimerization takes place here. The chromium ketenimine complex 20 is prepared by reaction of the Fischer-type chromium carbene complex with alkyl isocyanides.60 A cyclobutane-1,2,3,4-tetraimine 24 has been reported from the reaction of the ketenimine phosphonium ylide 22.61 Bisimine 23 has been proposed as the intermediate in this transformation. 

Initial attempts to form alkyl isocyanide complexes from metal atoms led to polymerization of the isocyanides (133). However, a recent report suggests that Ni(RNC)4, Fe(RNC)5, and Cr(RNC)6 can be made directly from the respective atoms and RNC at -196°C (98). 

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