Carbonyl group additions

Aldol Addition and Related Reactions. Procedures that involve the formation and subsequent reaction of anions derived from active methylene compounds constitute a very important and synthetically useful class of organic reactions. Perhaps the most common are those reactions in which the anion, usually called an enolate, is formed by removal of a proton from the carbon atom alpha to the carbonyl group. Addition of this enolate to another carbonyl of an aldehyde or ketone, followed by protonation, constitutes aldol addition, for example... 

Carbonylation (continued) of secondary alcohols, 34 94-96 (HRhIjCCO)] as active catalyst, 34 95 inhibitory effect of CO pressure, 34 94 2-propanol, 34 94 deuterium studies, 34 95 Carbonyl groups, addition of carbanions, 35 390-392... 

The starting reagent is the Reformatsky-typt. In this case, instead of adding to a carbonyl group, addition is to the nitrile. See Reformatskv Reaction for a discussion of reagent. 

Magnesium, 235 Samarium(II) iodide, 270 Titanium(IV) chloride, 304 Addition reactions to carbonyl groups—Addition of functionalized CARBON NUCLEOPHILES (see also Aldol reaction and other specific condensation reactions, Meth-ylenation, Peterson Olefination, Refor-matsky reaction, Wittig reaction, Wittig-Horner reaction)... 

The reduction of carbonyl compounds with metal hydride reagents can be viewed as nucleophilic addition of hydride to the carbonyl group. Addition of a hydride anion to an aldehyde or ketone produces an alkoxide anion, which on protonation gives the corresponding alcohol. Aldehydes give 1°-alcohols and ketone gives 2°-alcohols. 

Of the seven bands in the He I spectrum of COBrj (Fig. 17.15), only one (band F) exhibits any vibrational structure. The period of this structure (1690 cm [2028]) indicates that it is associated with stretching of the carbonyl group - additional support for the assignment of band F to ionization from an orbital with x(CO) character. 

The essential feature is the formation of a TiCl4—ketone complex which polarizes the carbonyl group. Addition of triethylamine yields a titanium enolate by proton abstraction. The enolate attacks a... 

Treatment of the methoxylactol (198) with ethanolic hydrazine afforded the novel ring-A-fused pyridazone (237). Diazomethane reacts sufficiently readily with iminium salts, e.g. (238), to allow the preparation of aziridinium salts (239) in the presence of diazomethane-sensitive carbonyl groups.Addition of cyanamide and halogen to 2- and 5-enes affords uic-halogeno-cyanoamines which give cyanoimines on contact with base. ... 

In the light of the VEH and MNDO calculations, the inierpretation ofPCL data is that A1 reacts first with carbonyl groups. Additional support for this view comes from XPS results. ... 

Whereas the cycloisomerization of allenic ketones affords achiral products, replacing the keto with a hydroxy group leads to the formation of chiral heterocycles. In 2001, the synthesis of chiral 2,5-dihydrofurans by treatment of a-hydroxyallenes with catalytic amounts of AuCls in unpolar solvents was reported (Scheme 4-90). Many functionalities (e.g., carbonyl groups, additional free alcohols, and acid-sensitive... 

In 2009, Chiba s group reported a manganese-mediated synthesis of pyridines from cyclopropanols with vinyl azides [70]. In the presence of 1.7 equivalents of Mn(AcAc)3, a variety of pyridine derivatives have been prepared in good yields at room temperature. In their further studies, they realized this transformation in a catalytic manner [71]. In their mechanistic studies, they found the reactions were initiated by a radical addition of /3-carbonyl radicals, generated by the one-electron oxidation of cyclopropanols with Mn(III), to vinyl azides to give imi-nyl radicals, which cyclized with the intramolecular carbonyl groups. Additionally, the application of this newly developed methodology in the synthesis of quaternary indole alkaloid, melinonine-E, was accomplished as well (Scheme 3.33). 

Other proposals [698] need allyl acetyl acetone 331 (or its ketal 332 of one carbonyl group). Addition of chlorocarbene to the free carbonyl gives the epoxide 333, which, under the strongly basic conditions of this reaction, rearranges to a highly functional ketoaldehyde 334, ready for aldol condensation to allethrolone (Reaction scheme 232) at a different position to that in the La Forge synthesis. 

Condensed formula Section 21.8 Carbonyl group Addition polymer... 

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