And the Mannich reaction

Aryl methyl ketones can only give a single enol (or enolate ion) and subsequent reactions are therefore entirely regioselective. These include halogenation (cf. Section 5.11.1, p. 667), and the Mannich reaction (cf. Section 5.18.2, p. 801). 

In addition to the 02 elimination reaction (17) and the Mannich reaction (14), phenoxyl/CV combination products can undergo a water elimination if the position where 02- has added to carries an H atom [e.g., reactions (20 and (21) d Alessandro et al. 2000]. 

A number of MCRs having enolate-derived nucleophilic components were subsequently discovered (Scheme 7.3), including the Hantzsch dihydropyridine synthesis [13], the Biginelli reaction [14, 15] and the Mannich reaction [16-20], An added complication in many of these MCRs is the potential irreversible addition of the nucleophile to the carbonyl component, leading to carbonyl addition products. Such MCRs, however, become feasible by the appropriate selection of components that do not favor such alternative transformations. For example, the use of formaldehyde is more effective in the Mannich reaction, because its greater reactivity towards the amine prevents its undesired reaction with the enolate component. 

Metal /3-diketonates, particularly acetylacetonates, will undergo electrophilic substitution at the central methine carbon atom in a similar way to aromatic compounds. Known reactions of this sort include bromination, nitration, acylation, and the Mannich reaction. 

Various imidazo[4,5-fc]pyrazin-2-ones (228) have been subjected to a number of different reactions. Alkylation, acylation and the Mannich reaction all give 1,3-disubstituted derivatives (229). Halogenation of the 2-oxo compound (230) with bromine or chlorine in acetic acid or with sulfuryl chloride provided monohalo derivatives (231) (69FRP1578366, 71BRP1248146). The chlorine atom of (231) can be removed by catalytic hydrogenation. 

The pyridazine ring is electron deficient and needs electron-releasing groups to facilitate electrophilic substitution. Reactions include nitration, halogenation (86SC543), protonation, and the Mannich reaction (84MI2). 

I. Aldolic addition and the Mannich reaction (Vol. I. p. 186) The aldolic I addition reaction of nitroalkanes with carbohydrates (specifically aldoses) continues to be an important reaction in sugar chemistry which according to Baer i ) in some respects surpasses in versatility limil Fischer s classical cyano-[hydrin syntliesis. Particularly noteworthy are publications by Baer and Kovaf 1144, 45], Funubaski. Yoshimura and co-workers (46 51] and other Japanese [workers (52], Russian workers [53, 54] and Bilik (55]. 

It has been foimd that a derivative of an alkylated hydroxyaro-matic compound derived from a conventional PIB and a high vinylidene PIB is equally effective and may be more effective as a fuel additive than a derivative of an alkylated hydroxyaromatic compound derived from a high vinylidene PIB. The preparation of a PIB alkylated phenol and the Mannich reaction runs as follows (27) ... 

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