1.3- dicarbonyl compounds reaction with benzyl

In the presence of a very strong base, such as an alkyllithium, sodium or potassium hydride, sodium or potassium amide, or LDA, 1,3-dicarbonyl compounds can be converted to their dianions by two sequential deprotonations.79 For example, reaction of benzoylacetone with sodium amide leads first to the enolate generated by deprotonation at the more acidic methylene group between the two carbonyl groups. A second equivalent of base deprotonates the benzyl methylene group to give a dienediolate. 

Nicardipine Nicardipine, l,4-dihydro-2,6-dimethyl-4-(3-nitrophenyl)-methyl-2-[(methyl-phenylmethyl)-amino]ethyl ester 3,5-pirididincarboxylic acid (19.3.7), is synthesized in a manner analogous to the synthesis of nifedipine, the only difference being that in the Hantsch synthesis, two different )3-dicarbonyl compounds are used simultaneously with o-nitrobenzaldehyde. During this, one of these in the enamine form of acetoacetic ester is simultaneously used as an amine component. A heterocycUzation reaction is accomplished by reacting, the methyl ester of 8-aminocrotonic acid with the 2-methyl-2-benzyl-aminoethyl ester of acetoacetic acid [24-27]. 

Thus, reaction of N-Cbz-protected a-, fl- or y-amino aldehydes 190 with 1,3-dicarbonyl compound 191 in the presence of benzyl enol ether 192 followed by hydrogenation led to substituted pyrrolidines, piperidines and azepanes as a mixture of diastereomers in >95% chemical purity in most cases. 

Reaction of halides with silver nitrate to give nitrate esters has been known for years, but its synthetic application is more recent. Komblum showed that the nitrate esters derived from a-bromo ketones and esters decompose smoothly with catalytic sodium acetate in DMSO to give the a-dicarbonyl compounds in high yield. It was found unnecessary to isolate the nitrate ester after reaction of the halide with silver nitrate the solution was filtered to remove AgBr, concentrated, and added to DMSO containing catalytic sodium acetate. The method complements the others for the synthesis of a-dicarbonyl compounds since it employs nonacidic, nonbasic conditions. Unfortunately, the method gave variable results with benzyl halides. The application of the method to bromo esters other than bromoacetates was not reported. Some related oxidations are shown in equations (41) and (42), and Schemes 9 and 10. The oxidation of an iminium salt is notable. 

The cyclizations of 85 to 86 and of 87 to 88 represent the simple cases in which the internal nucleophile is the OH group of an alcohol [64,65]. An in situ generated hydroxy group, as in the addition of alcohols to carbonyl compounds, can also participate in phenylseleno-etherification reactions. This is examplified by the conversion of 89 into 90 in the presence of benzyl alcohol [66]. Another type of OH, which gives rise to these reactions is the enolic OH of /1-dicarbonyl compounds. Thus, Ley reported that compounds like 91 and 93 can be transformed into the cyclic derivatives 92 and 94 by treatment with N-PSP 11 in the presence of zinc iodide [67]. The cyclization of 95 to 96 represents a simple example of the selenolactonization process [68, 69]. It is interesting to note that the various cyclization reactions indicated in Scheme 14, which require different electrophilic selenenylating agents, can all be effected with phenyselenyl sulfate [70]. 

Catalysis of benzylic bromination, see 1,3-Dibromo-5,5-dimethylhydantoin. Benzoyloxylation of malomc esters. Dibenzoyl peroxide reacts with the sodium derivative of diethyl ethylmalonate to give diethyl (O-benzoyl)ethyltartronate. This is a general reaction for /8-dicarbonyl compounds. 

Jorgensen developed a catalytic regioselective and enantioselective nucleophilic aromatic substitution reaction of activated aromatic compounds with 1,3-dicarbonyl compounds under phase-transfer conditions. This was crucial for obtaining the C-arylated product 61 predominantly with high enantioselectivity by replacing a benzyl with a benzoate group in the cinchona alkaloids-derived phase-transfer catalyst (Scheme 11.13) [49]. 

Knoevenagel reactions are used in the synthesis of a wide variety of O- and N-heterocycles. In the typical Knorr pyrrole synthesis, a 1,3-dicarbonyl compound is condensed with an oximino- or azimino-1,3-dicarbonyl compound followed by reductive cyclization. Thus, catalytic hydrogenation of benzyl acetoacetate (243) and diethyl oximinoacetonedicarboxylate (242) affords pyrrole (244), which is transformed to (245) by another Knoevenagel reaction (Scheme 49). A rational synthesis of all four uropor-phyrines has been achieved by cyclization of appropriate pyrroles such as (245). ° Another typical preparation of a heterocycle that involves a Knoevenagel condensation is the Hantzsch 1,4-dihydro-pyridine synthesis. Here, an aldehyde and two molecules of a 1,3-dicarl30nyl compound react in the... 

The picolinium salts (216) obtained by reactions of the picolines (215) with a-halogenoketones, and also with a-halogenoesters and a-halogenoni-triles (and even those from benzyl halides), react with a-dicarbonyl compounds in the presence of base to give quinolizinium salts (217) as shown in Scheme 50 salts derived from 1-methylisoquinoline similarly gave... 

Review. Oxidations with selenium dioxide have been reviewed (634 references). The reagent is useful for oxidation of carbonyl compounds to 1,2-dicarbonyl compounds, for oxidation of olefins to allylic alcohols, and for benzylic oxidations. It has been used for dehydrogenations, but high-potential quinones are probably more useful for this reaction. ... 

GSH can participate in free and bound form as a coenzyme of certain condensation and rearrangement type of reactions. Glyoxalase catalyzes the benzylic type of rearrangement of certain -dicarbonyl compounds with GSH as a coenzyme. 

Functionally substituted (77 -cyclopentadienyl)dicarbonyl iridium compounds were prepared from reactions of the corresponding substituted cyclopentadienyl-Na, -Li, or -T1 reagents with chlorodicarbonyl(pyridine)iridium. Ring-substituted compounds include chloro, benzyl, acetyl, carbomethoxy, methyl, benzoyl, trimethylsilyl, cyano, dimethylamino, tetra-Ph, dimethylaminoethyl, (tetramethyl)dimethylaminoethyl, methoxyethyl, pcntabenzyl, and pentamethyl. The symmmetric and antisymmetric carbonyl stretching frequencies as well as the NMR chemical shifts of the carbonyl substituents were correlated with various Hammett substituent parameters. ... 

Similar to the reaction with diarylpropene, the use of diarylpropynes enables propargylation of 1,3-dicarbonyl compounds to give 81 (Scheme 8.36). Oxidative C-C bond formations are also possible at the benzylic position in the case of reaction with 1,3-diaryl-l,3-diketones, and allylated and ben-zylated compounds 82 are obtained in moderate yields (Scheme 8.37). ... 

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