Syntheses and structural characterization of o-carboranylamides with direct cage–amide bond (original) (raw)

Reactions of lithio-o-carborane with isocyanates under various conditions were studied, and the structural features of the resulting carboranylamides are described. The reactions of o-carborane (o-C 2 B 10 H 12 ), n-BuLi (two equiv.) and two equiv. of (substituted) phenylisocyanate, pentylisocyanate and p-ethylphenylthioisocyanate in diethyl ether, respectively, led, after workup, to the corresponding mono-substituted carboranylamide 2a-g and carboranylthioamide 5 in low to moderate yields, and only with RNCO (R = Ph, m-MeOC 6 H 4 , pentyl) could disubstituted products 3a-c be isolated. The reaction with phenylisocyanate afforded the mono-amide and di-amide products in a ratio of approximately 1 : 2, whereas in the other two reactions the ratios are approximately 4 : 1 and 3 : 2, respectively. In tetrahydrofuran all the reactions attempted with RNCO (R = Ph, p-IC 6 H 4 , m-NCC 6 H 4 and pentyl) gave more monoamide products than those in diethyl ether. With phenylisocyanate no diamide product was isolated and with pentylisocyanate the ratio between monoamide and diamide is approximately 3.5 : 1. The new carboranylamides were characterized by means of elemental analyses, IR and NMR spectroscopy and mass spectrometry, as well as single-crystal X-ray diffraction analyses of 2a-f, 3a and 5. † Electronic supplementary information (ESI) available. CCDC 937467, 952824, 950184, 937468, 958414, 958415, 937469 and 963492. For ESI and crystallographic data in CIF or other electronic format see