Dihydropyrimidine-2,4-diones

A suspension ofWang resin (0.5 g, 0.88 mmol g ) in dry CH2CI2 (4 mL) was treated twice vdth triethylamine (200 pL) and then once with acryloyl chloride (100 pL) and allowed to stir for 2 h at rt. After filtration, the resin 66 was washed three times each with CH2CI2, methanol, DMF, methanol, and DMSO. The resin 66 was then treated with benzylamine (0.28 g, 2.6 mmol) in DMSO (2 mL) and allowed to stir for 24 h. The resulting resin 67 (P = Bn) was washed three times each with DMSO, methanol, and CH2CI2, and 

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AT-heterocycHc carbene ligands are generally most effective at promoting cycloadditions of this type (Scheme 3-28). Fully intermolecular versions of a related process are possible by the 2 1 coupling of isocyanates with allenes to produce dihydropyrimidine-2,4-diones. ... 

The Rh(I)/dppf complex-catalysed 2-i-2-i-2-cycloaddition of oximes and diynes formed substituted pyridines in moderate to good yields (88%), under mild conditions. A one-pot procedure has been developed using aldehydes.The Ni-catalysed 2 -I-2 -I-2-cycloaddition of isocyanates (117) with 1,3-dienes (118) in MeCN produced 6-substituted dihydropyrimidine 2,4-diones (119). A key intermediate in this reaction is a five-membered azanickelacyclic species (Scheme 35). " The enantioselective cationic Rh(I)-catalysed 2-i-2-i-2-cycloaddition of diynes and isocyanates formed axially chiral pyridones with high ees (82%). The unique source of chirality is provided by a system containing [Rh(cod)Cl]2, l,4-bis(diphenylphosphino)butane, and the silver phosphate salt Ag(5)-TRIP. " " The Rh-catalysed 2-I-2-I-2-cycloaddition of diynes to sulfonimines in DCE, at r.t. to 80 °C, yielded 1,2-dihydropyridines in good yields (54-86%) and enantioselectivity (61-96%... 

A three component condensation involving aryl amines, aldehydes, and olefins was used to assemble a variety of tetrahydroquinolines [83]. Dihydropyrimidine-2,4-diones were prepared from condensing amines with resin bound acrylates followed by treatment with isocyanates [84]. Two additional groups have published their work using the Pictet-Spengler reaction to prepare tetrahydro- -carbolines [85], tetrahydroisoquinolines [86] and... 

Koll996 Kolodziej, S.A. and Hamper, B.C., Solid-Phase Synthesis of 5,6-Dihydropyrimidine-2,4-diones, Tetrahedron Lett., 37 (1996) 5277-5280. 

Two somewhat different pathways exist for the conversion of 2,5-diamino-6-ribosylamino-4(3//)-pyrimidinone 5 -phosphate (2) into the substrate of lumazine synthase, 5-amino-6-ribitylamino-2,4(l//,3//)-dihydropyrimidine-dione (6). In fungi and Archaea (Figure 1, reaction IV), the ribosyl side chain of 2 is reduced under formation of... 

The chemical fixation of C02 in the presence of DBU or DBN led to l//-quinazoline-2,4-diones 115 <02T3155>, 5-acylated thiouracils 116a,b were obtained from pyridin-3- and 4-yl thioureas <02AJC287>, and dihydropyrimidines were obtained by an improved Biginelli reaction protocol... 

Dihydropyridines, Acridine-1,8-diones, 3,4-Dihydropyrimidine-2(lH)-ones, and Related Systems... 

In a ring-transformation reaction of the Sn-ANRORC type,275 l,3-dimethyl-2,4-dioxo-l,2,3,4-dihydropyrimidine-5-carbonitrile together with substituted acetonitriles affords 6-sub-stituted 7-aminopyrido[2,3-c/]pyrimidine-2,4(l//.3//)-diones.277 -27 3 This method is described in Section 7.2.2.1.1.2.4. 

In contrast, cyclic 1,3-diketones such as cyclohexane-1,3-dione having no stable OH O intramolecular hydrogen bonds in the enol form, react with 4,4-bis-(trifluoromethyl)-l,3-diazabuta-1,3-diene forming a mixture of 4,4-bis(tri-fluoro-methyl)-l,4-dihydropyrimidine 37 and 4,4-bis(trifluoromethyl)-4//-l,3-oxazine 38 (85CZ185) (Scheme 35). 

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