Iodine isocyanate, reactions

Iodine isocyanate was used to synthesize the first steroidal aziridine, 2, 3 -iminocholestane (95). from 5a-cholest-2-ene (91). This reaction sequence which is believed to proceed through a three-membered ring iodonium ion (92) illustrates the limitation of pseudohalogen additions for the synthesis of -aziridines. The iodonium complex forms from the least hindered side (usually alpha) and is opened tmK5-diaxially to give a -oriented nitrogen function. The 3a-iodo-2 -isocyanate (93) is converted by treatment with... 

Iodine azide, on the other hand, forms pure adducts with A -, A - and A -steroids by a mechanism analogous to that proposed for iodine isocyanate additions. Reduction of such adducts can lead to aziridines. However, most reducing agents effect elimination of the elements of iodine azide from the /mwj -diaxial adducts of the A - and A -olefins rather than reduction of the azide function to the iodo amine. Thus, this sequence appears to be of little value for the synthesis of A-, B- or C-ring aziridines. It is worthy to note that based on experience with nonsteroidal systems the application of electrophilic reducing agents such as diborane or lithium aluminum hydride-aluminum chloride may yet prove effective for the desired reduction. Lithium aluminum hydride accomplishes aziridine formation from the A -adducts, Le., 16 -azido-17a-iodoandrostanes (97) in a one-step reaction. The scope of this addition has been considerably enhanced by the recent... 

Significant amounts of the bicyclo[3.3.1]nonane adduct and of the octahydropental-enes were isolated also from the reaction of 3 with preformed iodine acetate and iodine acetate thallium (equation 75)94 whereas only the monocyclic 1,2-adducts were obtained from treatment of 3 with iodine azide, iodine isocyanate or iodine nitrate95. The different propensity to give transannular products with these latter reagents has been related to the different positive charge density on carbons in the corresponding iodonium ion intermediates. 

March82 has summerized the addition reactions of iodine isocyanate (IN=C=0) to C=C functions which were reported in the period 1963-1983. These reactions are similar to those with iodine azide described above. With IN=C=0, p-iodo isocyanates are formed (equation 55). As is the case with IN3, the addition is stereospecific and anti. The... 

Iodine isocyanate, preformed or made in situ from AgNCO and h, adds to alkeites - with the regio- and stneo-chemistry expected of reactions proceeding via cyclic iodonium ions. When the INCO is made in situ, a competing mechanism also occurs (except with the most reactive alkenes) in which the alkene complexes with the iodine, and the complex then reacts with the isocyanate ion to generate the same P-iodoisocyanate as obtained firom INCO direct The reaction can be carried out at -35 to +20 C in Et20, CHzCh, THF, pentane or excess alkene as solvent. Dichloromethane or ether are... 

The analogous reactions of alkenes with halogen azides are treated in Section 7.2.2 and those with iodine isocyanate and bromocyanamide are treated in Section 7.2.6. 

J-Iodo isocyanates were obtained by addition of iodine isocyanate or thiocyanate to al-kenes45 61. Iodine isocyanate is generated by adding iodine to a suspension of silver cyanate in diethyl ether at — 15°C. When an alkene is present in the reaction medium, anti addition takes place and /J-iodo isocyanates result in good yield52. 

This stereochemical character is shared by all addition reactions involving a halonium ion, so that mixed halogens e.g. Br-F [8g], Br Cl [go], I Cl [gi] and I F [g2]), and also reagents like hypobromous acid (Br-OH) [gs], acetyl hypobromite (CH3CO OBr) [g4] and iodine isocyanate (I NCO) [gs] lead to diaxial addition products, with the... 

Episulfides. Hinshaw reasoned that addition of an alkene to such solutions should give jS-iodothiocyanates in analogy with the reaction of iodine isocyanate (1, 501 2, 223-224 . 3, 161 -16.3) with alkenes. indeed treatment of cyclohexene with iodine thiocyanate gives a /5-iodothiocyanate (2), which on treatment with methanolic... 

Iodine isocyanate, IN=C=0. Mol. wt. 168.93. Preparation from silver cyanate and iodine. The reagent adds to olefins in the trans manner to give iodo-isocyanates," of interest because they can be transformed into ethyleneimines." The reaction is... 

Swern8 has determined the relative rates of reaction of iodine isocyanate with a variety of unsaturated compounds the results are consistent with an electrophilic reaction. Although it is convenient to use reagent prepared in situ, this reagent is unsatisfactory in the case of acetylenes, which react preferentially to form diiodo compounds.9 In this case it is preferable to use a preformed solution of the reagent, prepared as follows.10 An excess of silver cyanate is treated with iodine in ether, THF, or glyme at — 30° in the dark. Such material reacts at least 10 times faster with olefins than the reagent prepared in situ. 

Addition to alkenes. The addition reaction of iodine isocyanate to alkenes is much faster in methylene chloride than in ether, the commonly used solvent. The... 

Aziridines can be obtained from alkenes using iodine isocyanate or iodine azide. The product from the latter reaction can be converted into the aziridine via reduction, or into an azirine via elimination of hydrogen iodide and pyrolysis. " ... 

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