1.5- Diazabicyclo pyrimidine

Valence Isomerization of Diazabicyclo[4.2.0]octatrienes From Pyrimidines... 

Similar treatment of 5-nitrobenzothiadiazole 97 with ethyl isocyanoacetate and l,8-diazabicyclo[5.4.0]undec-7-ene (DBU) gave the thiadiazolo[3,4-< ]isoindole 93 (21%), but when a phosphazene base was employed the major isolated product was the pyrimidine fV-oxide 98 (46%) (Equation 13) <1996J(P1)1403, 1996TL8391>. 

The pyrido[2,3- pyrimidinones 380 and 381 were thermally obtained from boiling the ethyl acrylate derivatives 378 and 379, respectively, with l,8-diazabicyclo[5.4.0]undec-7-ene (DBU) and EtNHPd in THF (Scheme 13) <2001W02001055148, 2004USP2004009993>. The acrylates were obtained from reaction of the corresponding pyrimidine-5-carbaldehyde with (carbethoxymethylene)triphenylphosphorane. On the other hand, acrylate 382 was converted into 383 via aza-Wittig cyclization (Equation 32) <1997LA1619>. 

Lithium diisopropyl amide (LDA) assisted Thorpe-Ziegler cyclization of cyanoenolethers (11) was used to synthesize the ribose-C-glycoside 12, which was further transformed into a furo[3,2-d] pyrimidine (86TL815 90MI1). Other bases such as NaOEt, l,5-diazabicyclo[4,3,0] non-5-ene (DBN), r-BuOK or n-BuLi that were successfully used in pyrrole syntheses (see Section III. A) were not suitable for this furan formation (Scheme 3). 

Reaction of 2-oxopyrido[l,2-a]pyrimidines (33) with /f-oxo esters in dimethylformamide in the presence of l,5-diazabicyclo[4,3,0]non-5-ene at room temperature, or with /Toxo amides in the presence of zinc chloride in boiling ethanol, affords the pyridone derivatives (199). Cleavage of the pyrimidine ring can also be effected with amines.28... 

The hydroxy group of l-(2-hydroxyethyl)thieno[3,4-d]pyrimidine-2,4(3//)-dione 344 was chlorinated with thionyl chloride in a mixture of pyridine and chloroform, or mesylated with methanesulfonyl chloride in pyridine. No ring chlorination was observed under these conditions. The resulting l-(2-chloro or 2-methanesulfonylethyl) derivative 365 was cyclized to l,2-dihydrooxazolo[2,3-6]thieno[3,4-d]pyrimidin-5-one 366 with 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) (89H985). A similar transformation of 3-(2-hydroxyethyl)thieno[3,4-d]pyrimidine-2(l//),4-diones 333a,b into the 3-(2-chloroethyl) derivatives 367 with thionyl chloride occurred in chlo-... 

The authors postulated a di-re-methane mechanism for the photochemical isomerization, with the formation of 2,4-diazabicyclo[3.1.0]hex-2(3)-ene (123) as an intermediate. Subsequent opening of the three-membered ring with a concomitant [1,5]-hydrogen shift from nitrogen to C-2 gave 2,5-dihydro-pyrimidine 124 [Eq. (57)]. 

Cbz Cp DABCO DBU DDQ (DHQD)2CLB (DHQD)2PYR DMF DME DMPU DMSO Et Fmoc HMPA ia KHMDS LDA LiHMDS Me MEM Ms NaHMDS Ph Piv PMB Pr Py (saltmen)Mn(N) benzyloxy carbonyl p 5 -cyclopentadienyl l,4-diazabicyclo[2.2.2]octane l,8-diazabicyclo[5.4.0]undec-7-ene 2,3 -dichloro-5,6-dicyanobenzoquinone dihydroquinidinyl p-chlorobenzoale (see Chart 1) dihydroquinidinyl pyrimidine (see Chart 1) dimethylformamide dimethoxyethane l,3-dimethyl-3,4,5,6-tetrahydro-2(l//)-pyrimidinone dimethylsulfoxide ethyl 9-fluorenylmethoxy carbonyl hexamethylphosphoric triamide inverse addition potassium hexamethyldisilazide lithium diisopropylamide lithium hexamethyldisilazide methyl (2-methoxy ethoxy )methyl methanesulfonyl sodium hexamethyldisilazide phenyl pivaloyl p -methoxy benzyl propyl pyridine nitrido[A,A/-(l,l,2,2-tetramethyl) bis(salicylideneaminato)]manganese (see Chart 1)... 

The acrylic acid ester side chain may also be introduced by the Wittig reaction of 6-chloro-l,3-dimethyl-2,4-dioxo-l,2,3,4-tetrahydropyrimidine-5-carbaldehyde with the appropriate ylide. Subsequent conversion to a 6-amino compound and ring closure in the presence of triethyl-amine gives 8-alkyl-l,3-dimethylpyrido[2,3-t/]pyrimidine-2,4,7(l//,3//,8W)-triones 9. 45 146 Exclusive formation of pyrido[2,3-t/]pyrimidines is achieved by refluxing the acrylic acid esters in a mixture of triethylamine and dimethylformamide in the presence of l,5-diazabicyclo[4.3.0]-non-5-ene (DBN).147 55t... 

The interaction of 2-alkylthio-A -thiazoline and 3-methyl-4-p-chloro-phenylthio-2-azetidinone (175) (in the presence of catalytic amounts of l,4-diazabicyclo[2,2,2]octane) at 120 X under nitrogen affords 16% yields of 6-methyl-5-oxo-5H-2,3-dihydrothiazolo[3,2-a]pyrimidine (176). This and analogous reactions of the azetidinone are promoted by the good leaving properties of its arylthio-group. " ... 

A large excess of benzaldehyde and a little NH4-bromide added to a mixture of frans-2-nitrophenyl-3-benzoylaziridine and commercial abs. ethanol, satd. with NHg, stoppered, and stored at least 3 days at room temp. 2,4-diphenyl-6-p-nitrophenyl-l,3-diazabicyclo[3.1.0]hex-3-ene. Y 92%. F. e. and reactions, such as rearrangement to pyrimidines, s. H. W. Heine et al., J. Org. Ghem. 32, 2708 (1967). 

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