1.3- Dimethyl-3,4,5,6-tetrahydro-2 -pyrimidone

If the ,v-3,6-dimethyl-3-te -butyl-tetrahydro-4(3/f)-pyrimidone 3 is enolized and alkylated, only the diastereomer 4 is formed22. 

BASF AG CRBPII dba DBN DBU DIBAL-H DMAP DMF DMF-DMA DMPU HMDS HMPA HMPT H-LR LDA LDE LRAT MCPBA MOM NMO NMP PCC PhH = Badische Anilin- Soda Fabrik AG = cellular retinol-binding protein type II r dibenzylideneacetone = 1,5-diazabicyclo[4.3.0]non-5-ene = l,8-diazabicyclo[5.4.0]undec-7-ene = diisobutylaluminium hydride = 4-dimethylaminopyridine = A V-dimethylformamide = A,V-dimethylformamide, dimethylacetal = 1,3 -dimethyl-3,4,5,6-tetrahydro-2( 1H)-pyrimidone = hexamethyldisilazane = hexamethylphosphoramide = hexamethylphosphorous triamide = Hoffmann-La Roche = lithium diisopropylamide = lithium diethylamide = lecithin retinol acyltransferase = m-chloroperbenzoic acid = methoxymethyl = iV-methylmorpholine oxide = l-methyl-2-pyrrolidinone = pyridinium chlorochromate = benzene... 

DMPU l,3-Dimethyl-3,4,5,6-tetrahydro-2(lEi)-pyrimidone DMSO Dimethylsiflfoxide Fmoc 9-Fluorenylmethoxycarhonyl HASC a Heteroatom-suhstituted carhonyl... 

The complexity of the solvation of lithium bases has also been demonstrated by studies of LiNPr 2 mediated ester enolization of Bu -cyclohexanecarboxylate in four different solvents (THF, Bu OMe, HMPA/THF and DMPU/THF (DMPU = l,3-dimethyl-3,4,5,6-tetrahydro-2(lH)-pyrimidone)). Even when experiments are designed to exclude mixed aggregate effects, four different mechanisms with nearly identical rates are observed, involving ... 

A striking exaple of the influence of the Schlenk equilibrium on the progress of reactions of organomagnesium compounds was observed in, what was named, a ligand-assisted nucleophilic addition reaction (LANA), in which the substrate was a lithium quinol alkoxide [29]. In a typical LANA reaction (Scheme 14) the lithium quinol alkoxide is first prepared in situ, after which follows the sequential addition of l,3-dimethyl-3,4,5,6-tetrahydro-2(l//)-pyrimidone (DPMU) and a Grignard reagent. 

DMPU 1,3-dimethyl-3,4,5,6-tetrahydro-2(1 /-/)-pyrimidone (A/,A/-dimethyl propylene urea) I... 

A cobalt-catalysed insertion of 1-alkene, 2-alkene, and styrene into the ortho C-H bond of benzamides, such as (94), has been attained by using l,3-dimethyl-3,4,5,6-tetrahydro-2(l/7)-pyrimidone (DMPU) as a key ligand, and cyclohexylmagnesium chloride. The reaction proceeds at 25 °C to afford the < rt/io-alkylated product (95) selectively. ... 

Because of their usefulness in aldol additions and other synthetic methods (see especially Section 6.5.2), there has been a good deal of interest in the factors that control the stereoselectivity of enolate formation from esters. For simple esters such as ethyl propanoate, the E -enolate is preferred under kinetic conditions using a strong base such as LDA in THF solution. Inclusion of a strong cation solvating co-solvent, such as HMPA or tetrahydro-l,3-dimethyl-2(l//)pyrimidone (DMPU) favors the Z-enolate. ... 

The cyclic urea known as DMPU (l,3-Dimethyl-3,4,5,6-tetrahydro-2(H)-pyrimidone or N,N -dimethylpropyleneurea), has been demonstrated by Seebach and colleagues in Switzerland to closely reproduce the solvent capabilities of HMPA. Moreover, with a structure quite different from HMPA, DMPU was found to be non-mutagenic and non-carcinogenic when tested to determine if it might cause similar genetic and chronic health effects and, therefore, was proposed as a safe replacement. Based on successful substitution of DMPU for HMPA, as shown in the following reaction schemes, DMPU can be recommended as a possible replacement for HMPA wherever possible in large-scale commercial processes. 

A route to a,P-unsaturated primary amides 14 can be allowed through the palladium-catalyzed reaction of vinyl iodides/triflates with carbon monoxide in the presence of hexamethyldisilazane followed by hydrolytic workup (Scheme 9.6) [30]. To suppress the formation of by-products, the choice of the solvent played a pivotal role and satisfactory yields of the target products 14 were obtained with 1,3-dimethyl-3,4,5,6-tetrahydro-2(lH)-pyrimidone (DMPU) at 80-100°C. The use of 4 mol of PPhg per mole of palladium was found necessary to prolong the lifetime of the catalyst. 

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