Reactions, with carbonyls

Although several experimental data concerning the functionalization of cumulenic anions are availab. a (for a review see Ref. 10) (Table I), it remains difficult to predict the compos tion of the product of a particular reaction on a rationalistic basis. Especially the outcome of reactions with carbonyl compounds seems to be... 

Reaction With Carbonyl Compounds. Primary and secondary nitroparaffins undergo aldol-type reactions with a variety of aldehydes and ketones to give nitro alcohols (11). Those derived from the lower nitroparaffins and formaldehyde are available commercially (see Nitro alcohols). Nitro alcohols can be reduced to the corresponding amino alcohols (see Alkanolamines). 

A-Substituted pyrroles, furans and dialkylthiophenes undergo photosensitized [2 + 2] cycloaddition reactions with carbonyl compounds to give oxetanes. This is illustrated by the addition of furan and benzophenone to give the oxetane (138). The photochemical reaction of pyrroles with aliphatic aldehydes and ketones results in the regiospecific formation of 3-(l-hydroxyalkyl)pyrroles (e.g. 139). The intermediate oxetane undergoes rearrangement under the reaction conditions (79JOC2949). 

Pyrazolones show a great variety of reactions with carbonyl compounds (B-76MI40402). For instance, antipyrine is 4-hydroxymethylated by formaldehyde and it also undergoes the Mannich reaction. Tautomerizable 2-pyrazolin-5-ones react with aldehydes to yield compound (324) and with acetone to form 4-isopropylidene derivatives or dimers (Scheme 8 Section 4.02.1.4.10). 

There have been few mechanistic studies of Lewis acid-catalyzed cycloaddition reactions with carbonyl compounds. Danishefsky et ah, for example, concluded that the reaction of benzaldehyde 1 with trans-l-methoxy-3-(trimethylsilyloxy)-l,3-di-methyl-1,3-butadiene (Danishefsky s diene) 2 in the presence of BF3 as the catalyst proceeds via a stepwise mechanism, whereas a concerted reaction occurs when ZnCl2 or lanthanides are used as catalysts (Scheme 4.3) [7]. The evidence of a change in the diastereochemistry of the reaction is that trans-3 is the major cycloaddition product in the Bp3-catalyzed reaction, whereas cis-3 is the major product in, for example, the ZnCl2-catalyzed reaction - the latter resulting from exo addition (Scheme 4.3). 

Allylboron compounds have proven to be an exceedingly useful class of allylmetal reagents for the stereoselective synthesis of homoallylic alcohols via reactions with carbonyl compounds, especially aldehydes1. The reactions of allylboron compounds and aldehydes proceed by way of cyclic transition states with predictable transmission of olefinic stereochemistry to anti (from L-alkene precursors) or syn (from Z-alkene precursors) relationships about the newly formed carbon-carbon bond. This stereochemical feature, classified as simple diastereoselection, is general for Type I allylorganometallicslb. 

It undergoes many condensation and addition reactions with carbonyl compds, active methylene compds, and activated olefins (Refs 10,43,... 

In this section alkylation, Michael additions, hydroxyalkylation (reaction with carbonyl compounds), aminoalkylation, acylation and some other reactions of a-sulphinyl carbanions will be discussed. 

Reaction of a-phenylsulfinyl acetate or ethyl a-(t-butylsulfmyl)acetate with one equivalent of ethylmagnesium bromide or iodide was shown to give the corresponding Grignard reagent 129 or 132, which upon reaction with carbonyl compounds afforded the corresponding adducts. Thus Nokami and coworkers prepared ethyl / -hydroxycarboxylates 130167, jS-keto esters 131168, a,/J-unsaturated esters 133169 and other derivatives by this method. 

The mixed lithium aminophosphonium azadiylides 7 [47] are known to be involved in reaction with various electrophiles specifically at the carbon center. The reaction with carbonyl known to form betaine adducts was recently used for the first time in Wittig type reactions for the synthesis of di-, tri-, and tetrasubsti-tuted alkenes 8 [52]. 

Among other olefins prepared in conventional ylide reactions with carbonyls are (68), (69), (70), and (71). ... 

The decarboxylation reaction usually proceeds from the dissociated form of a carboxyl group. As a result, the primary reaction intermediate is more or less a carbanion-like species. In one case, the carbanion is stabilized by the adjacent carbonyl group to form an enolate intermediate as seen in the case of decarboxylation of malonic acid and tropic acid derivatives. In the other case, the anion is stabilized by the aid of the thiazolium ring of TPP. This is the case of transketolases. The formation of carbanion equivalents is essentially important in the synthetic chemistry no matter what methods one takes, i.e., enzymatic or ordinary chemical. They undergo C—C bond-forming reactions with carbonyl compounds as well as a number of reactions with electrophiles, such as protonation, Michael-type addition, substitution with pyrophosphate and halides and so on. In this context,... 

Bioreactors containing an nndefined anaerobic consortinm rednced TNT to 2,4,6-triaminotoluene (TAT) in the presence of glncose (Dann et al. 1998). The sorption of TAT to montmorillonite clay was irreversible, and the snbstrate conld not be released by solvent extraction or by acid or alkaline treatment. Similar resnlts were obtained with humic acids in which covalent reactions with carbonyl or activated C=C bonding presumably occurred. Results from laboratory experiments nsing i C-labeled TNT in reactors to which... 

The availability of the tetrahalogenoanthranilic acids, in particular tetrachloroanthranilic acid, suggested that an investigation of reactions with carbonyl compounds would be worthwhile. The reactions of arynes... 

Other aromatic heterocycles undergo Patemo-Btichi reaction with carbonyl compounds, although these reactions have seldom been applied to organic synthesis. For example, thiophene reacts cleanly with benzaldehyde to afford a single exo product in 63% yield87. Pyrroles also react with aldehydes and ketones however, as a result of the lability of the presumed initial cycloadducts, the only products isolated, even with the rigorous exclusion of acid, are the 3-hydroxyalkylpyrroles 200 (equation 7)89. 

Song and Beak161 have used intramolecular and intermolecular hydrogen-deuterium kinetic isotope effects to investigate the mechanism of the tin tetrachloride catalysed ene-carbonyl enophile addition reaction between diethyloxomalonate and methylenecy-clohexane (equation 105). These ene reactions with carbonyl enophiles can occur by a concerted (equation 106) or a stepwise mechanism (equation 107), where the formation of the intermediate is either fast and reversible and the second step is slow k- > k-i), or where the formation of the intermediate (the k step) is rate-determining. 

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