Acetophenone nitro-substituted, reduction

The response of the peroxybenzoates to the CIEEL activators depends remarkably on the nature of the substituent. The unsubstituted peroxybenzoate [29a] behaves in a fashion nearly identical to that observed for the peroxyacetate [28]. The p-methoxy-substituted peroxybenzoate [29b] behaves quite like the parent, but the nitro-substituted compounds [29d] and [29e] and the p-dimethylamino-substituted peroxybenzoate [29c] behave quite differently. The properties of these compounds, however, can be understood within the CIEEL mechanism. For example, the nitro-substituted peroxybenzoates [29d] and [29e] with DMAC exhibit a value of k2 approximately ten times greater than for the unsubstituted peroxide. Yet the yield of excited singlet DMAC generated by [29d] and [29e] is 700 times less than from 29a. This seeming inconsistency can be easily understood. In the postulated CIEEL path, the reduction of the peroxide results in its fragmentation to acetophenone and an acid. One of these species must be a radical anion. For the peroxyacetate and all of the substituted peroxybenzoates examined, with the exception of the nitro-substituted examples, the more easily reduced species of this pair is... 

Condensation of methyl ketones with (3 -dimethylaminonitroethylene gives y-nitro-a,/3-unsaturated enones which can be reductively cyclized to pyrroles. This method was first applied to substituted acetophenones, giving 2-arylpyrroles (equation 84) (74CB1499, 71CB440). 

Since the first asymmetric reduction of ketones with chiral borohydrides by Itsuno et al. [ 1 ], a number of studies on the asymmetric reduction of ketones with chiral borane reagents have been demonstrated [2]. Corey s oxazaborolidines are some of the most successful reagents [3 ]. The effect of fluorine substituents was examined in the asymmetric reduction of acetophenone with LiBH4 by the use of chiral boronates (73) obtained from substituted phenyl boronic acid and tartaric acid [4]. Likewise, 3-nitro, fluorine, and trifluoromethyl groups on the 3- or 4-position provided enhanced stereoselection (Scheme 5.20). 

Buchwald and co-workers observed the persistent formation of 2-nitrophenols in an attempted arylation with reactive o-chloronitroarenes. They found an unusual effect of phenolic additives, and developed an annulative proach to highly substituted indoles. The arylation of acetophenone with 3-nitro -chlorobenzoate proceeded smoothly in the presence of 20 mol% 4-methoxyphenol and K3PO4 to give 25, which was methylated without isolation. Reduction of the methylated ketone 26 with TiCls afforded 2,3-disubstituted indole 27 in 61 % overall yield [22]. 

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