Reaction with malonates

An other procedure for constructing this ring system started with 2-methylbenzimidazole 583 whose reaction with malonic ester 584 gave 585... 

The cz5-aziridine substrate shows, as expected on the basis of this model, predominant formation of the trans-cyclopropane product. The starting materials for this MIRC reaction can readily be obtained from the aziridine esters by reduction to the corresponding aldehyde and a subsequent Knoevenagel reaction with malonate ester (Scheme 25) [34]. 

Previous work [111] by our group has demonstrated that RTIL-catalyzed 1,3-dipolar cycloaddition under the action of microwave irradiation leads to dramatically shorter reaction times with better yields of isolated products. We have recently investigated the reactivity of the formyl group covalently grafted on the ionic liquid phase 75 in the Knoevenagel reaction with malonic derivatives 76 [112], as shown in Scheme 8.76. 

These model reactions were of great value in the extension of the C-glycosylation reaction with malonic esters to five-membered ring-systems. Treatment of 2,3 5,6-di-O-isopropylidene-a-D-manno-furanosyl bromide122,123 (150) with diethyl sodiomalonate led to an anomeric mixture of C-glycosyl compounds that could be separated by column chromatography, with the a (151) and /B (152) anomers in... 

The all-trans annulenes can also be obtained by performing the Bingel reaction with malonates such as XCH(C02Et)2 (X= NO2 or S02CH2Ph) [72]. 

The Pechmann and Knoevenagel reactions have been widely used to synthesise coumarins and developments in both have been reported. Activated phenols react rapidly with ethyl acetoacetate, propenoic acid and propynoic acid under microwave irradiation using cation-exchange resins as catalyst <99SL608>. Similarly, salicylaldehydes are converted into coumarin-3-carboxylic acids when the reaction with malonic acid is catalysed by the montmorillonite KSF <99JOC1033>. In both cases the use of a solid catalyst has environmentally friendly benefits. Methyl 3-(3-coumarinyl)propenoate 44, prepared from dimethyl glutaconate and salicylaldehyde, is a stable electron deficient diene which reacts with enamines to form benzo[c]coumarins. An inverse electron demand Diels-Alder reaction is followed by elimination of a secondary amine and aromatisation (Scheme 26) <99SL477>. 

Monocyclic l,4-diazepin-5-ones and fused l,5-benzodiazepin-2-ones, e.g. (169) and (170), can be readily prepared by the reactions of 1,2-diamines with / -ketoesters (67AHC(8)21, p. 57, 68CRV747, p. 776, 71JHC797). Similarly reactions with malonic acids and esters give l,4-diazepine-5,7-diones (171) (67AHC(8)2l, pp. 55,69,68CRV747, p. 78l>. 

Table 8. Electrogenerated superoxide reaction with malonate esters ...

---