Isocyano group

In a like manner the 6/3-isocyano group can be utilized to activate the C(6) proton (79JCS(P1)2455), an example of which is shown in Scheme 43. It was also possible to introduce the 6a-methylthio substituent by reacting the intermediate anion with methyl methoxycarbonyl disulfide The 6a-methylthio group could subsequently be converted to the 6a-methoxy group by treatment with CI2 and MeOH. 

Benzimidazole with [Cr(CO)5CNCCl3] gives the A, A -earbenes 109 and 110, the produets of simultaneous attack at trichloromethyl and isocyano groups simultaneously (95JOM(489)27). The probability of the formation of the primary product [Cr(CO)5(C(L)N=CCl2] is low (88AGE1344, 89ZN(B)1414). 

When the reaction is run with potassium fert-butoxide in THF at -5°C, one obtains (after hydrolysis) the normal Knoevenagel product (32), except that the isocyano group has been hydrated (16-65). With the same base but with DME as solvent the product is the nitrile (33). When the ketone is treated with 31 and thallium(I) ethoxide in a 4 1 mixture of absolute ethanol and DME at room temperature, the product is a 4-ethoxy-2-oxazoline (34). Since 33 can be hydrolyzed to a carboxylic acid and 34 to an a-hydroxy aldehyde, this versatile reaction provides a means for achieving the conversion of RCOR to RCHR COOH, RCHR CN, or RCR (OH)CHO. The conversions to RCHR COOH and to RCHR CN have also been carried out with certain aldehydes (R = H). 

The preparation of helically well-ordered polymers with stable screw-sense, which is able to be transmitted to newly formed polymer main-chains effectively, is highly desired for the development of new methodology for the synthesis of optically active helical polymers. An aromatizing polymerization of 1,2-diisocyanobenzenes is promoted by methylpalladium(II) complexes, producing poly(quinoxaline-2,3-diyl)s.146-148 The polymerization proceeds with successive insertion of the two isocyano groups of the diisocyanobenzene to the carbon palladium bond of... 

Zinc complexes of a fused pyrroloporphyrin, cyclopropanochlorin, that contain an appended isocyano group show dimer formation. The X-ray structure reveals five-coordinate zinc centers... 

Since the discovery of this new class or marine metabolites, the origin of the isocyano group and its relation to its congeners has continued to draw the interest of investigators. While the chemical transformations of these functions are firmly established, progress in understanding the biogenetic details within the -NC/-NCS/-NHCHO series has been slow. 

Stylotelline (23) is a constituent of a Stylotella sp. collected offshore in New Caledonia. 13C NMR spectra involving 2D NMR techniques provided the bulk of information leading to its structure. The absolute configuration was demonstrated after the tertiary isocyano group was removed to yield the known conjugated diene, ( + )-d-selinene (24). Optical rotation and spectral data of the transformation product were identical in all respects to those of the corresponding product obtained from eudesmols [42], Although neither the isothiocyanato nor the formamido compounds were isolated, the latter was prepared, which allowed an nOe observation between the axial C-3 and the amide protons. 

Reaction of the tetrasilanes with 1.5 equiv. of aryl isocyanide affords a four-membered ring product, in which all the Si-Si bonds and the carbon-nitrogen bond of the isocyano group are cleaved and reorganized (Equation (54)).135... 

The isocyano group has been found to be linear within 1° at the nitrogen atom in isocyanocyclopropane202 (126). The structure has been determined from the MW spectra with some assumptions (Table 11). There is little difference between distal and vicinal bonds the latter are slightly elongated compared to 1. 

Finally the isocyano group is formed by elimination of water. 

The formation of linear bridges implies basicity on the N atom of a MCN group and indeed methylation or protonation can occur to give isocyano groups, MCNMe,... 

The barrier to the inversion imposed by the isocyano group permitted the evaluation of the effect of gegenion, solvent and temperature on this cyclopropyl anion. As is evident from Table 27 only at — 5°C is the loss of configuration very rapid. This would be consistent with the view that there is a great deal of ionic character associated with the lithium-carbon bond ... 

Hence, in the case of the electronegative isocyano group which possesses a Tc-system for delocalization (as the carbonyl and the nitrile group) but additionally a non-bonding pair of electrons on nitrogen, even a free or naked anion is capable of maintaining its configuration. 

In the laboratory of T.-L. Ho, the total synthesis of the novel marine sesquiterpene (+)-isocyanoallopupukeanane was completed." In the endgame of the synthesis, it was necessary to install the isocyano group onto the tricyclic trisubstituted alkene substrate so that it will occupy the more substituted carbon atom (according to Markovnikov s rule). The Ritter reaction was chosen to form the required carbon-nitrogen bond. The alkene substrate was dissolved in glacial acetic acid and first excess sodium cyanide followed by concentrated sulfuric acid was added at 0 °C. The reaction mixture was stirred at ambient temperature for one day and then was subjected to aqueous work-up. The product A/-alkyl formamide was subsequently dehydrated with tosyl chloride in pyridine to give rise to the desired tertiary isocyanide which indeed was identical with the natural product. 

There is another, rather unusual, functional group that is related to the cyanide group. It contains a carbon atom that is only doubly bonded to a nitrogen atom, but which is not involved in any further bonding. This is the isocyano group, RNC. Draw the dot and cross structure of this grouping. 

The peptide-based isocyanides 50a-e were successfully polymerized by Ni(II) catalysts under an inert atmosphere [63-66]. An alanine-derived isocyanide, whose isocyano group was labeled using 13C and 15N, was prepared and successfully polymerized for structure elucidation [67]. Several solvent systems were used in the polymerization of the peptide-based isocyanides, depending upon the solubility of the isocyanides. As mentioned earlier, the use of alcohols as a solvent or co-solvent can accelerate the polymerization. The protective groups on the ester, hydroxy, and imidazole groups were removed after polymerization by treatment with aqueous NaOH to yield poly(isocyanide)s bearing unprotected peptide side chains. 

Isocyanides bearing ammonium side-chains 51 and 52 have been polymerized in the presence of nickel catalysts [72, 73]. The amphiphilic isocyanide 51 forms vesicles on dispersion in water. The isocyano groups located in the vesicle bilayers were polymerized by nickel capronate to form polymerized vesicles. The isocyanide 51 was also used in the preparation of polymerized vesicles containing metalloporphyrin components within the bilayer membrane [74]. The redox behavior of this membrane-bound cytochrome P-450 mimic has been investigated in detail. In addition to those bearing cationic side chains, isocyanides 53 and 54 bearing zwitterionic side chains were successfully used [75]. 

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