A new procedure for the preparation of some IV-alkyl-and JV-aralkylmaleimides has been developed. This procedure uses the reaction of a heavy metal salt of maleimide with alkyl and aralkyl halides in an inert solvent. Silver maleimide (3) was found to be far more reactive than mercuric maleimide (2). Compound 3 was prepared by treatment of maleimide with silver nitrate and sodium hydroxide in a mixture of ethanol and dimethyl sulfoxide. Compound 2 was prepared by treatment of maleimide with mercuric chloride and sodium hydroxide in ethanol-water. The latter reacted with trityl chloride in refluxing toluene to give a 60% yield of Ntritylmaleimide (4). The reaction of 3 with trityl chloride in benzene at room temperature increased the yield to 95%. Compound 3 was treated with benzhydryl bromide, benzyl bromide, -bromo-p-xylene, and 9-bromofluorene in benzene under reflux to yield IV-benzhydrylmaleimide (5, 57%), IV-benzylmaleimide (6, 38%), a-Nmaleimidyl-p-xylene (7, 17%), and TV-(9-fluorenyl)maleimide (8, 55%), respectively. JV-(l-Adamantyl)maleimide (9) was prepared in refluxing toluene in a 51% yield. When this last reaction was run at room temperature, 0-(l-adamantyl)maleimide (10) was obtained in nearly quantitative yield. This compound represents the first synthesis of an O-alkylmaleimide and it can easily be distinguished from 9 and other N-substituted maleimides by nmr, ir, and uv spectroscopy, and by tic. Compound 10 was converted to 9 in a 55% yield by heating the compound in toluene in the presence of silver bromide.
22)Opening at the less substituted carbon has been called the "normal" mode while opening at the more substituted carbon has been called the "abnormal" mode (cf. ref 18-20). Since this terminology is backwards for carbocation reactions, its use here would be confusing. We recommend that such terminology not be perpetuated.
9-Acetoxybicyclo[3.3.l]nona-2,6(7)-diene (18), a versatile intermediate for t h e synthesis o f heteroatom substituted adamantanes, was prepared in eight steps f r o m the commercially available 1,4-cyclohexanediol. T h i s intermediate m a y be used in t h e synthesis o f substituted oxa-, aza-, a n d thiaadamantanes. Utility o f this intermediate was shown by synthesis o f 2-oxa-6-adamantanol (19), 2-oxa-6-adamantanone (22), 2-oxa-6-adamantanamine hydrochloride (23), a n d 2-oxa-6-adamantanecarboxylic acid (26).
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