Hoffman intermediate

The reaction of benzoylnitrene with lithium bromide was studied to determine whether a nitreneoid [PhCON(Li)Br] or a Hoffman intermediate (PhCON-Br) would be formed.79 Time-resolved IR spectroscopy combined with DFT modelling indicated that the Hoffman intermediate is formed. 

Industrial synthesis of vitamin A (Hoffman-La-Roche) goes through partial hydrogenation of an enyne (equation 161)277. A number of syntheses of pheromones, where the reduction of an enyne to a diene is the key step, have been devised. A few selected examples are given in Table 29278. During the total synthesis of endiandric acids, Nico-laou employed hydrogenation of a polyenyne intermediate with a Lindlar catalyst to generate an intermediate which underwent symmetry-allowed cyclizations to result in the natural product (equation 162)279. 

Davydov, R., Makris, T.M., Kofman, V., Werst, D.E., Sligar, S.G. and Hoffman, B. M. (2001) Hydroxylation of camphor by reduced oxy-cytochrome P450cam mechanistic implications of EPR and ENDOR studies of catalytic intermediates in native and mutant enzymes. Journal of the American Chemical Society, 123, 1403-1415. 

Limited information from animal studies suggests that intermediate- or chronic-duration exposure to disulfoton is not associated) with hematological effects. No hematological effects were observed in rats fed <0.55 mg/kg/day of disulfoton (Klotzsche 1972) or in mice fed <0.71 mg/kg/day (Rivett et al. 1972) for 90 days. In 2-year feeding studies, disulfoton did not cause any hematological effects in rats (Carpy et al. 1975 Hayes 1985), mice (Hayes 1983), or dogs (Hoffman et al. 1975). 

Mills, G. and Hoffman, M.R. Photocatal34ic degradation of pentachlorophenol on Ti02 particles identification of intermediates and mechanism of reaction,/hvzron. 5ci. Technol, 27(8) 1681-1689, 1993. 

Attempts to prepare 2,3,5,6-tetraaminopyrazine (91) by Hoffman degradation of the diamide (88) were unsuccessful. This is apparently due to both intermolecular and intramolecular urea formation from the intermediate isocyanate giving a mixture of products, which upon attempted hydrolysis to 91 undergo a significant amount of attack on the pyrazine ring (70UP1). 

Hoffman, R. V. Organic Chemistry An Intermediate Text. 2nd Edition. John Wiley Sons, Inc., Hoboken, NJ, 2004. 

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