Benzylidene-, diethyl

Reaction of 2-aminopyridine and its 4-methyl derivative and diethyl alkylidenemalonates 356 at 175°C for 1.5-2.5h yielded 3-vinyl derivatives 358, after the isomerization of the exocyclic double bond in 357 (99ACS901). Reaction of 2-amino-4-methylpyridine and bis(2,4,6-trichlor-ophenyl) benzylidenemalonate in the presence of NEt3 afforded only non-cyclised product 359. 2-Aminopyridine and its 4-methyl derivative with diethyl benzylidene- and hexylidenemalonates at 190 °C did not give cyclized products (99ACS901, 99MI29). 

The synthesis of the right-wing sector, compound 4, commences with the prochiral diol 26 (see Scheme 4). The latter substance is known and can be conveniently prepared in two steps from diethyl malonate via C-allylation, followed by reduction of the two ethoxy-carbonyl functions. Exposure of 26 to benzaldehyde and a catalytic amount of camphorsulfonic acid (CSA) under dehydrating conditions accomplishes the simultaneous protection of both hydroxyl groups in the form of a benzylidene acetal (see intermediate 32, Scheme 4). Interestingly, when benzylidene acetal 32 is treated with lithium aluminum hydride and aluminum trichloride (1 4) in ether at 25 °C, a Lewis acid induced reduction takes place to give... 

The simple cleavage of lactones 1 or 2 with alcohol and acid has not been reported. However, when 1 is treated with benzaldehyde diethyl acetal and hydrochloric acid, ethyl 3,5 4,6-di-0-benzylidene-L-gulonate (47) is formed in >90% yield.77,78 No other isomers were observed, and other acetals of benzaldehyde, as well as aliphatic aldehydes, afford similar products in good yield.77 D Addieco prepared36 similarly protected derivatives of L-gulonic acid by oxidation of l,3 2,4-di-0-ethylidene-D-glucitol (15), followed by esterification of the resulting acid with diazomethane. 

The activated Ba(OH)2 catalyst was successfully used for the Michael reactions of chalcone with active methylene compounds 290), as well as for the Michael reaction of other benzylidene derivatives of acetone, butanone, 3-methylbutanone, 4-methyl-2-pentanone, and 3,3-dimethylbutanone with ethyl acetoacetate and diethyl malonate. The reaction with diethyl malonate gave good yields of the Michael adduct (between 65 and 93%), whereas with ethyl acetoacetate various products were obtained, depending on temperature and amount of catalyst (Scheme 43) 291). Thus, by varying the reaction conditions, it was possible to obtain a single product with practically 100% selectivity, the yields being higher than those obtained with soluble catalysts, such as KOH, NaOH, or piperidine. 

Alternatively, when 21 was treated with benzaldehyde diethyl acetal-hydrochloric acid, ethyl 3,5 4,6-di-0-benzylidene-L-gulonate (76) was formed in >90% yield. Diacetal 76 was efficiently oxidized to 77 (>90% yield) with dimethyl sulfoxide-trifluoroacetic anhydride, or by way of the nitrate of 76 and triethylamine. Hydrolysis of 77 then afforded ethyl L-xy(o-2-hexulosonate in 86% yield.383... 

The inner disaccharide unit of the trisaccharide hapten of the M. avium serovar 8 GPL148 was assembled in a manner similar to that of the serovar 20, but with reaction of the rhamnosyl trichloroacetimidate (80b) with the benzylidene acetal (81). O-Deacetylation of the product yielded the disaccharide acceptor (84) for the next glycosylation. Incorporation of the pyruvate acetal moiety into the terminal 3-O-methyl-D-glucose residue of 85 was achieved by transacetalation with methyl pyruvate diethyl dithioacetal, with sulfuryl chloride-triflic acid as catalyst. From the mixture of products the desired diastereomer was separated and converted by successive O-debenzylation, acetylation, selective 1-O-deacetylation, and reaction with trichloroacetonitrile into the trichloroacetimidate 86. Reaction of glycosyl donor 86 with acceptor 84, with trimethylsilyl triflate as promoter, afforded fully... 

Protonation of sodium phenylethynetellurolate by hydrogen chloride in diethyl ether led to 1,3-ditelluretane derivatives2 4 via cyclodimerization of the tellurol. 3,5-Dibenzylidene-1,2,4-tritellurolane was also isolated3. Protonation of sodium phenylethynetellurolate with trifluoroacetic acid affords 2-benzylidene-4-phenyl-l,3-ditellurole5. 

The intermediate VII formed from the starting compound and diethyl-aminosulfur trifluoride reacts by an SN2 mechanism to yield a product with inversion of configuration on carbons 1 and 2, 2-benzyl-3-azido-4,6-0-benzylidene-3-deoxy- 3-D-allopyranosyl fluoride (IV) [8]. 

Lefebvre and Evans found that lithium diethyl phosphite [(EtO)2POLi] adds to (Ss)-N-benzylidene-p-toIuenesulfinamide (126) to give (Ss,S)-128 in 85% yield and 84% de.77 The diastereomeric excess was improved to 93% de by using the sodium salt and to >97% with lithium diisopropyl phosphite. Transition state 127, involving si-face attack of the nucleophile, was proposed to account for the favored formation of 128. a-Aminobenzyl phosphonic acid 129 was obtained on hydrolysis of 128.78 Similar results were reported for the addition of diamido phosphite to 126.78... 

Dissolve 2,3-O-benzylidene-L-tartrate, L-4 (64 g, 225 mmol) in diethyl ether (200 mL) in a dry stoppered flask, and transfer the resulting solution to the pressure-equalising addition funnel. 

A solution of trichloroacetimidate 2-azido-3-0-benzyl-4,6-0-benzylidene-2-deoxy-n-glucopyranoside (3.217mmol) and l-D-l,2-0-(r.-l,7,7-trimethy][2.2.1 -bicyc]ohept-2-ylidene)-3,4-0-(l,l,3,3-tetraisopropyldisiloxanyl)-myo-inositol (4.507mmol) in 50 ml diethyl ether at —20°C was treated with 29 ml trimethylsilyl trifluromethanesulfonate, then gradually warmed over 5 hours to ambient temperature. The mixture was then quenched with 0.5 ml triethylamine and concentrated. The residue was purified by flash chromatography using a hexane/EtOAc gradient of 95 5-75 25 and the a(l-6) product isolated in 55% yield as a white solid. 

As described here, both enantiomers of 3 can be prepared In three steps from commercially available diethyl D- and L-tartrate in up to 70% over-all yield.2 3 5 Procedures to obtain the benzylidene acetal,11 12 with the ensuing reduction step,11. 2 are based on previous literature reports. Both enantiomers of 3 have been used in highly stereoselective nitroaldol additions.3 13 Imines, nitrones, oximes, and nitrile oxides derived therefrom were recently employed in a variety of additions/cycloadditions.14 15 (-)-2-0-Benzyl-L-glyceraldehyde has further been used... 

Diethyl (-)-2,3-0-benzylidene-L-tartrate 1,3-Dioxolane-4,5-dicarboxylic acid, 2-phenyl-, diethyl ester, [4R-(2a.4a,5P)]- (9) (35572-31-7)... 

An eight-stage synthesis of 2-methylbenzomorphan (115) from benzal-dehyde via diethyl benzylidene malonate (110) in 19% overall yield has been reported<52) (Scheme 4,17). The amino radical precursor, N-chloramine (111),... 

Bis-[methoxy-methyl]-diethyl- -chlorid E14a/2, 180 (N-Methoxymethylierung) (a-Brom-benzyliden)-dialkyl- E5, 39 (R — CO — NR2 + COBr2)... 

Carbohydrate moieties have also been used as chiral auxiliaries in the addition of dialkyl phosphites to the C = N bond. Thus, 0-pivaloylated iV-benzylidene-/ -D-galactosylamine reacts with diethyl phosphite to give four diastereomeric esters (the a and (i forms not shown), in which those with the S configuration at the newly created stereogenic center prevail69. 

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