Organic Lab Reactions 284

Organic Lab Reactions 284 - tially the same(60-80 M As has...

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REDUCTION WITH HYPOPHOSPHOROUS ACID 279 refrigerator or room temperature. 81 Although deaminations have been carried out at the boiling point of the reaction mixture it does not appear that such a high temperature is to be recommended. 85 Hydrochloric and sulfuric acids have been employed with about equal frequency in hypophosphorous acid reductions. Recent work has shown that, in "general, the reaction goes more smoothly with the diazonium chlorides, 82 so that, with certain exceptions discussed below, diazotiza- tion with hydrochloric acid is advisable. The striking results obtained with the tqluidines are recorded in Table I. The isomeric nitroanilines TABLE I DEPENDENCE OF THE YIELD OF TOLUENE ON THE ACID USED FOB DIAZOTIZATION Toluidine Acid Used for Diazotization Yield oriho meta para do not display this sensitivity to the acid used for diazotization; with either hydrochloric or sulfuric acid, the yields of nitrobenzene are essen-
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Unformatted text preview: tially the same (60-80%). M As has already been noted in the section on ethanol deaminations, upon diazotizing some nitroamines in hydrochloric acid, a diazonium salt is obtained in which the nitro group has been replaced by chlorine (pp. 272-273). Consequently, hypophosphorous acid reduction gives a deaminated product containing chlorine in place of the nitro group. For example, when 5-amino-8-nitroisoquinoline (XVIII) is diazotized with hydrochloric acid and then treated with hypophosphorous acid, 8-chloro-isoquinoline (XIX) is obtained in 60-70% yield instead of 8-nitro-isoquinoline. 88 NH 2 HCl H 2 SO 4 HCl H 2 SO 4 HCl H2SO4 70-75% 12-23% 51-62% 5-12% 77-83% 27-29% 88 Bellavita, Atti congr. nazl. chim. pura applicata, 5th Congr., Rome, 1935, Pt. I, 294 (1936) [C. A., 31, 3901 (1937)]. M Keilen and Cass, J. Am. Chem. Soe., 64, 2442 (1942). -...
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