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Aromatic substitution is one of the most thoroughly studied reactions.[1] Yet in spite of the wealth of mechanistic knowledge and numerous synthetic applications, this paper reports a facile and hitherto unknown alkylation procedure for nitroaromatics.When p-dinitrobenzene (1) is treated with trialkylborane in the presence of potassium tert-butoxide in tert-butyl alcohol at room temperature for five minutes, it furnishes p-alkylnitrobenzene (2, Equation 1) in high yield. Equivalent amounts of the three componentsÐ1, trialkylborane, and baseÐwere found to be essential for the completion of the reaction. When the amount of trialkylborane or base is reduced below this ratio, the substrate is consumed in an amount equivalent to the reagent present in the minimum concentration. Since an excessive amount of base results in the formation of p-tertbutoxynitrobenzene, a small excess (approximately 10 %) of the borane reagent was usually employed. When the reaction was performed with triethylborane, by-products 3 ± 6 were isolated in addition to 70 % of 2 (R Et, Scheme 1). Scheme 1. By-products obtained in the reaction of p-dinitrobenzene with triethylborane.The reaction can also take place in THF. However, the yields are slightly lower with the major difference being the presence of approximately 15 % of p-tert-butoxynitrobenzene amongst the products. Using two equivalents of triethylborane increased the yield to 85 % and no p-tert-butoxynitrobenzene was formed. Temperature sensitivity was also observed. When the reaction was conducted at temperatures below 25 8C the rate decreased drastically. At 0 8C, for example, the reaction does not progress, to a significant extent, even after 2 hours.Using tributylborane, the yield of p-butylnitrobenzene was also in the range of 70 ± 80 % and no isomerization on the butyl chain was observed. However, the reaction failed with triphenylborane. Even after 24 hours no para phenylation was observed. When the substrate was changed to p-nitrobenzaldehyde and the previous reaction conditions were employed in THF, only 7 % of 2 (from departure of CHO) was observed after 12 hours.Aluminum, the homologue of borane, was found to be much less reactive. Treatment with triethylaluminum, under identical reaction conditions gave only 19 % (NMR yield) of p-ethylnitrobenzene after 12 h at room temperature although over 40 % of 1 was consumed.The reaction is unlikely to be a radical or a radical ± anionic chain mechanism of a type similar to the Srn1 reaction [2] since it also proceeds smoothly in 2-propanol, a solvent which rapidly reacts with free radicals. In addition, no inhibition of the reaction by 5 mol % galvinoxyl is observed and the reaction is not catalyzed by the laboratory light. On the other hand, p-dinitrobenzene is known to be a powerful electron acceptor [3] and trialkylboranes are known to yield very rapidly, with a rate constant of 10 8 m À1 s À1, alkyl radicals when reacted with oxy-radicals.[4] Based on the nature of the reactants and the aforementioned results a tentative noncha...

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Lithium perchlorate/diethyl ether (LPDE) mediated rearrangement of α- and β-endo-dicyclopentadienyl vinyl ethers 5 and 6 resulted in the formation of the aldehyde 8, indicating that the mechanism is nonconcerted and the recombination of the ion pair occurs at the dissociated stage and not the intimate ion-pair stage. Proof of this came from deuterium-labeling studies and the use of an optically pure starting material. Furthermore, that the ionic intermediate formed must be symmetrical resulting in enantiomeric aldehydes from both normal and allylic attack corresponding to products of formal 1,3 and 3,3 shifts was seen in the chiral analysis of the benzoate derivative of the aldehydes formed from the optically pure vinyl ether.