Dibenzyl malonate

Cyclopropyl-3-fluoro-2-hydroxy-6-oxo-6//-pyrido[l,2-n]pyrimidine-7-carboxylates 340 were obtained in the reaction of 2-cyclopropyl-2-(5-fluoro-4-hydroxy-2-pyrimidinyl)acetaldehyde (339) and ethyl, rerr-butyl and dibenzyl malonates in the presence of piperidine and AcOH (95MIP1, 96JMC3070, 96MIP4, 96USP5580872). 

When the reaction was performed in diethyl malonate as the solvent, there were formed the acetal 156 and another product, which was assigned structure 157. The same type of product was formed when dibenzyl malonate was the solvent. A plausible mechanism for... 

Moreover, these rare earth heterobimetallic complexes can be utilized for a variety of efficient catalytic asymmetric reactions as shown in Scheme 7 Next we began with the development of an amphoteric asymmetric catalyst assembled from aluminum and an alkali metal.1171 The new asymmetric catalyst could be prepared efficiently from LiAlH4 and 2 mol equiv of (R)-BINOL, and the structure was unequivocally determined by X-ray crystallographic analysis (Scheme 8). This aluminum-lithium-BINOL complex (ALB) was highly effective in the Michael reaction of cyclohexenone 75 with dibenzyl malonate 77, giving 82 with 99% ee and 88 % yield at room temperature. Although LLB and... 

Scheme 20 Conjugate addition of dibenzyl malonate to a, P-unsaturated ketones...

Scheme 6.132 Representative Mannich adducts obtained from the base-catalyzed in situ generation of N-protected aldimines from N-Boc- and N-Cbz-protected a-amido sulfones and subsequent 121- and 124-catalyzed addition of dibenzyl malonate. The product configurations were not determined.

Zinc dibenzyl malonate complex 129, prepared by the action of Et2Zn on dibenzyl malonate, was found to be superior to alkali metal dibenzyl malonates, in terms of enantiomeric control, in the allylic substitution with ( )-130 catalysed by an in situ prepared Pd-(/ )-BINAP complex (equation 73)164. 

Cyclopropane and lactone functions can be prepared by the same double alkylation protocol as shown in Scheme 8E.12 [64], Both dibenzyl malonate and Meldrum s acid served well as nucleophiles to give excellent enantioselectivities. While subjecting the malonate adduct 95 to the second alkylation generated cyclopropane 96, the alkylation of the Meldrum s adduct 97 under similar conditions produced lactone 98 via an unusual O-alkylation. 

Potassium bromide Sodium nitrite Dibenzyl malonate Hydroxy benztriazole... 

Dibenzyl malonate (124.5 g, 0.44 mol) was taken up in dry DMF and potassium t-butoxide (49.2 g, 0.44 mol) was added portionwise with stirring and cooling. When a homogeneous solution had formed it was cooled to 0°C, then t-butyl-2R-bromo-5-methylpentanoate (110.1 g, 0.44 mol) in DMF (200 ml) was added dropwise over 1 h. When addition was complete the reaction was transfered to a cold room at 5°C and left for 4 days. The reaction mixture was partitioned between ethyl acetate and saturated ammonium chloride then the aqueous layer extracted with further ethyl acetate (4 x 500 ml), drying and solvent removal left an oil (228.0 g) heavily contaminated with DMF. This oil was taken into ether (1 L) and washed with brine (2 x 11) then the organic layer dried (magnesium sulfate), solvent removed under reduced pressure to leave the benzyl (2-benzyloxycarbonyl-3R-(t-butoxycarbonyl)-5-methylhexanoate (179.0 g) contaminated with a small amount of dibenzyl malonate. 

In 2002, Sasai et al. reported the synthesis of dendritic heterobimetal-lic multi-functional chiral catalysts, containing up to 12 l,l/-bi-2-naphthol (BINOL) units at their terminal positions (Fig. 9) [30]. On treating these functionalized dendrimers with AlMe3 and n-Buli, insoluble metallated Al-Ii-bis(binaphthoxide) generation x (GX-ALB) catalysts were obtained, which showed moderate catalytic activity in the asymmetric Michael reaction of 2-cyclohexenone with dibenzyl malonate (Scheme 4). 

Scheme 4 Asymmetric Michael reaction of 2-cyclohexenone with dibenzyl malonate catalyzed by the metallated dendrimer shown in Fig. 9...

Park, S.Y., Morimoto, H., Matsunaga, S., and Shibasaki, M. (2007) Catalytic asymmetric Munich reactions of dibenzyl malonate to a 3-unsaturated N-acylpyrroles using a La(OIV)3/Ph-hnked-BlNOL complex. Tetrahedron Letters, 48, 2815-2818. 

The hydrogenolysis of benzyl esters provides a means for the selective eonversion of the ester to the acid under mild conditions. Substituted dibenzyl malonates are easily converted to the substituted malonic acids by hydrogenolysis in neutral medium thus avoiding the acyl cleavage or decarboxylation which can result from base or acid catalyzed ester hydrolysis (Eqns. 20.26-27).5 . 58 Monobenzylmalonates are selectively debenzylated and decarboxylated to give the substituted acetic esters. 

La-linked-BINOL complex 23 was introduced as a stable, storable, and reuse-able asymmetric catalyst for the Michael reaction [120]. Optimization of the reaction between dibenzyl malonate and 2-cyclohexene-1-one in DME afforded the Michael adduct in 94% yield and >99% ee. The extraordinary versatility of LnLB catalyts is also documented in the highly efficient Michael addition of thiols to a,y9-unsaturated carbonyl compounds [121] and tandem Michael-aldol reactions [122]. 

Dibenzyl malonate, CH,(C02CH2C6H5)2. Mol. wt. 284.30, b.p. 188°/0.2 min. Preparation in 5% yield by refluxing malonic acid, benzyl alcohol, and a trace of sulfuric acid in toluene under a constant water separator (method A ). The ester is sensitive to heat and should be distilled rapidly through a short-path system. ... 

The steroidal glucoside ginsensoside Rgi 152 can be selectively monoacylated in high yields at the 6 -position using Candida antarctica lipase as the biocata-lyst1261, 2621. In this case, similar results were obtained with different acyl donors such as vinyl acetate, dibenzyl malonate and bis(trichloethyl) malonate (Fig. 18-20). 

Kumamoto, T., Rhine, K., Endo, M. et al. (2005) Guanidine-catalysed asymmetric addition reactions Michael reaction of cyclopentenone with dibenzyl malonates and epoxidation of chalcone. Heterocycles, 66, 347-359. 

---