3-Aryl-2,4-dioxo

Solid-supported a-bromoketone 148 was condensed with various 2-aminopyridines or 2-aminopyrimidine derivatives to give imidazo[l,2-a]pyridines or imidazo[l,2-fl]pyriniidine derivatives 149 after cleavage with acid <03TL6265>. An abnormal aza-Wittig reaction on solid-phase parallel synthesis of 3-aryl-2,4-dioxo-l,3,5-triazino[l,2-a]benzimidazoles was observed <03TL3705>. New spiroimidazolidinone derivatives 151 were prepared Irom SynPhase lanterns from dipeptides anchored on the solid-supports 150 <03JCO356>. 

Resin-bound iminophosphoranes 103 derived from the reaction of resin-bound 2-aminobenzimidazole 102 with triphenylphosphine oxide were reacted with aryl isocyanates in an abnormal aza-Wittig reaction with a chemoselectivity that depends on the reaction temperature and the nature of the aryl isocyanate (Scheme 22). The mechanism considered for the solid phase synthesis reaction involves the loss of triphenylphosphin-imide instead of triphenylphosphine oxide, resulting in the formation of isocyanates instead of carbodiimides as intermediates. Optimization studies revealed that employing electron-poor aryl isocyanates at high temperature leads to 95% of the abnormal aza-Wittig products 3-aryl 2,4-dioxo-l,3,5,-triazino[l,2-fl]benzimidazoles 104 [76]. 

Alkyl and 6-aryl derivatives of 3,5-dioxo-2,3,4,5-tetrahydro-l,2,4-triazine or of its thio analogs have been mentioned before in this review (e.g., Section II,B,2,a). Some of theih contained functional... 

The lithium enolate of AUV-dimethylacetamide underwent addition to 2-aryl-1-nitroethenes to give /faryl-y-nitroamides. The lithium dianions and the trianions of /l-oxo esters and /i,y-dioxo esters undergo addition to 2-aryl-1-nitroethenes to give bicyclic compounds as a single dia-stereomer8. 

Dioxo-l,3-diaryl-propane dimerisieren reduktiv zu 3,4-Dihydroxy-1,6-dioxo-1,3,4.6-tetra-aryl-hexanen I, 1,3,5,6-Tctraaryl-2,4,7-trioxa-tricyclo[3.2.1.13 6]n0nanen II und 1,2,4-Trihydroxy-l,2,4-triaryl-3-aroyl-cyclopentancn III4 ... 

Thermolysis of 3-alkyloxy- and 3-aroyloxy-5-phenyl-l,2,4-pyrrolo[l,2- ]quinoxaline-l,2,4-triones afforded 5-phenyl-9-(4-phenyl-3-oxo-3,4-dihydro-2-quinoxalinyl)-6,8,10-trioxo-5,6,9,10-tetrahydro-87/-pyrido[l,2-tf ]quinoxaline-7,9-dicarboxylates <2000CHE615, 2004CHE1295> and 7-aroyl-8-aroyloxy-5-phenyl-9-(4-phenyl-3-oxo-3,4-dihydro-2-quinoxalinyl)-5,6-dihydro-1077-pyrido[l,2- ]quinoxaline-6,10-diones <2002CHE498>, respectively. Thermolysis of 3-aryl-2-(5-aryl-2,3-dioxo-2,3-dioxo-4-furanyl)quinoxalines gave 7-aroyl-8-aroyloxy-6-aryl-9-(3-aryl-2-quinoxalyl)-10/7-pyrido[l,2- ]quinoxalin-10-ones <2001CHE1314, 2002RCB850>. 

In contrast to thermal uncatalyzed reactions of /V-acylsulfinylamines with aryl isocyanates which give rise to azoarenes,188 the cobalt or iron carbonyl-catalyzed process gives additionally 3,5-dioxo-l,2,4-triphenyl-1,2,4-triazolidine (Scheme 124).189 The only possible restriction on this simple urazole synthesis would be the expectation that the substituents on the reactants must be the same to prohibit exchange. 

The reactions of 4,6-dioxo-2-methyl-2-(4-nitrophenyl)-l, 3-dioxane (441, R1 = Me, R2 = 4-N02Ph), ethyl orthoformate, and anilines in boiling acetic acid for 5 min gave arylaminomethylenemalonates (442, R = aryl, R1 = Me, R2 = 4-N02Ph) in 65-70% yields [78ZN(B)I550]. 

Hydrazination of 4-aryl-3,5-dioxo-2,3,4,5-tetrahydro-l,2,4-triazine (66) also affords a rearranged product, 4-amino-3,5-dioxo-2,3,4,5-tetrahydro-1,2,4-triazine (81JHC953). This replacement of the A-aryl group by the N-amino group requires the intermediacy of the ring-opened compound 67. This intermediate could be isolated under mild conditions and its structure was proven by an independent synthesis. From this structure it can be concluded unequivocally that the ring transformation involves initial addition of the hydrazine at C-5 and not at C-3 (Scheme III.37). 

Arylidene-substituted Meldrum s acids 290 were reacted with 5-amino-6-phenyl-3(2//)-pyridazinone 291 to yield 4-aryl-2,5-dioxo-8-phenyl-l,2,3,4,5,6-hexahydropyrido[2,3-r/]pyridazines 292 in one step in good yields... 

N-Alkyl-aniline und Diphenylamin gehen mit 1,4-Dioxo- und mit 2,6-Dimethyl-l, 4-dioxo-cyclohexan eine saure-katalysierte Kondensation ein, die zu Alkyl-diaryl- bzw. zu Tri-aryl-aminen fuhrt diese Reaktion stellt insgesamt eine N-Arylierung dar2. 

Ar aryl, frequently including heteroaryl quinone = 4,5-dichloro-3,6-dioxo-... 

Oxidation of 3,4-dihydropyrimidin-2(l //)-oncs (DHPMs) with ceric ammonium nitrate (CAN) in acetic acid resulted in ethyl 2,4-dioxo-6-phenyltetrahydropyrimidin-5-carboxylates as the major product. However, DHPMs undergo a regioselective oxidation with CAN in the presence of sodium hydrogencarbonate in neutral aqueous acetone solution to yield ethyl 6-meihyl-4-aryl(alkyl)pyrimidin-2(l //)-one-5-carboxylates. A mechanism involving a nitrolic acid intermediate has been suggested.72... 

The self condensation of a-carbonyl ketenes also constitutes a type (i) synthesis of 2//-pyran-2-oncs. Cyclophanes 627 are synthesized by the thermal decomposition of bis(4,6-dioxo-l,3-dioxanes) 628 and dimerization of the resulting bis(a-carbonyl ketenes) 629 (Scheme 141) <1999JA8270>. Similarly, thermal decomposition of 4,5-diarylfuran-2,3-diones 630 forms the intermediate a-carbonyl ketenes, which dimerize to afford 3,4,5-aryl-2//-pyran-2-ones (Scheme 142) <2003RJ0103>. 

As yet no satisfactory syntheses to form dibenzothiocines were noted (as in CHEC-II(1996)). However, using intramolecular Heck coupling between aryl halide and acrylate moieties in 17 affords l,l-dioxo-2//-dibenzo[ /] thiocine-5-carboxylic acid ethyl ester 18 in 69% yield (Scheme 5) <20040L3005>. 

Several alkyls and aryls with M=0 (or M=NR) groups have been characterized. A simple methyl, OsOMe4 is obtainable from 0s04. The dioxo alkyl, 0s02(CH2Bu )2,125 can be converted into alkylidene and alkylidyne compounds,... 

Similar syntheses of arylated 1,3-dioxo-cyclohexanone derivatives also lead to arylated phenols. The enolic methoxyl group of the enolketone is removed using lithiumaluminiumhydride. Acetone cyanhydrin transforms the enolic methoxyl group into a cyano group. Arylated cyano phenols are also available109) by this route ... 

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