Vicinal tricarbonyls

Substituted derivatives of l-(tetrahydrobenzo[b]thiophen-2-yl-3-carboxylate)-5-phenyl-6-thio-l,2,4-triazin-4-one have been synthesized by heterocyclization reactions of different hydrazones obtained from 2-amino-tetrahydrobenzo[b]thiophene-3-carboxylate with phenyl isothiocyanate <00PS275>. Reaction of 5-methyl isothiosemicarbazide with a-amino acid vicinal tricarbonyl reactive substrates 1 and 2 yields 1,2,4-triazine substituted a-amino acids, as an equimolar mixture of regioisomers 3a/3b and 4a /4b, respectively <00JCS(P1)299>. 

Scheme 31 Oxidation of 2,3-dihydroxyesters to vicinal tricarbonyl compounds with bromide and 80.

Carboximidoyl chlorides may be reacted with oximes to give 30-65% yield of amidines, which may then be used to form imidazoles in good yields, by treatment with TsOH (equation 201)716. Highly substituted imidazoles may be prepared in a simple one-pot synthesis by treating vicinal tricarbonyl compounds with an aldehyde and ammonium acetate (equation 202)717. The reaction occurs in 66-90% yield and seems to be general in scope. 

Diketones 253 and -keto esters 254, with the same procedure, were converted into the corresponding monoprotected vicinal tricarbonyl compounds 255 and 256, respectively (Scheme 40) [120]. Whenever the group linked to ketonic carbonyl was a methyl (R = Me), the diprotected vicinal tetracarbonyl compounds 257 and 258 were produced. The formation of these products represents a further example of the easiness with which the MeCO group is converted into the a-keto acetal under these experimental conditions. 

Wasserman, H. H., Ennis, D. S., Vu, C. B., Schulte, G. K. Benzilic acid rearrangements in the reactions of aryl vicinal tricarbonyl derivatives with aldehyde Schiff bases. Tetrahedron Lett. 1991,32, 6039-6042. 

Fretz has prepared a L-phenylalanine derivative substituted with a keto-ylide (149). The ylide function of 149 acts as a stable precursor to a vicinal tricarbonyl moiety which is readily obtained by oxidation of the phosphoranylidene group with oxone. Ylide 149 has been utilized in the solid-phase synthesis of peptides containing the vicinal tricarbonyl moiety. ... 

Reactions of cyclic and acyclic 1,2,3-triones with phenylhydrazine give rise to mono- and bis-(phenylhydrazones). The central carbonyl group of a vicinal tricarbonyl system is electron-deficient and highly electrophilic,255 which is why treatment with an aryldiazonium ion affords 2-phenylhydrazones. The structure of such bis(phenylhydrazones) as cyclopentane-1,2,3-trione 1,3-bis(phenylhydrazone), dehydroascorbic acid 2,3-bis(phenylhydrazone), and cy-clobutanetetraone l,3-bis(phenylhydrazone) has been studied by UV, IR,1H-, 13C-, and 15N-NMR spectroscopy.265-268 Quantum-mechanical calculations to predict the most stable tautomeric forms of some 1,2- and l,3-bis(phenylhydrazones) revealed that the chelated bis(hydrazone) structure was usually more stable than the azoene-hydrazine structure.269-271 This does not mean that such structures do not exist, for example cyclobutanetetraone l,2,3-tris(phenylhydrazone) exists in a stable phenylazoene-hydrazine structure (see 49 Scheme 8).257-263... 

Fig. 11 Reversible conformational rearrangement upon reduction of vicinal tricarbonyl (9).

Hanefeld and coworkers179 have recently noted that the reaction of sulfenes generated in situ from sulfonyl chlorides and tertiary amines, with vicinal tricarbonyl compounds such as indan-l,2,3-trione, alloxane, diethyl mesoxalate and 1-methyl-1,2,3,4-tetrahydroquinoline-2,3,4-trione, afford products derived mainly from ring opening of /i-sultones (equation 139). 

Vicinal tricarbonyl compounds have been obtained from 2,3-dihydroxy-alkanoic esters with NaBr02 in combination with 4-benzoyloxy-2,2,6,6-tetramethylpiperidin-1-oxyl. In an alternative method bromide ion is used to mediate electrooxidation. Epoxidation of alkenes. This reaction proceeds at room temperature in the... 

Wasserman HH, Amici RM (1989) The Chemistry of Vicinal Tricarbonyls. A Total Synthesis of ( )-3-Demethoxyerythratidinone. J Oig Chem 54 5843 Padwa A, Hennig R, Kappe CO, Reger TS (1998) A Triple Cascade Sequence as a Strategy for the Construction of the Erythrinane Skeleton. J Oig Chem 63 1144, and lit cited therein... 

The He-I photoelectron spectra of vicinal tricarbonyl molecules, including (28) and its bicyclo[3,2,l] analogue, have been studied. The first two bands for (28) are interpreted in terms of the ionization of an electron from lone pair combinations of the 2p-oxygen orbitals. The dispirocyclopropyl derivatives (29) and (30) exhibit pronounced interaction between the antisymmetric Walsh orbitals the monospiro-cyclopropyl compounds were studied for purposes of comparison. " Inductive effects... 

Sn 1-active alkyl halides require longer reaction times (typically 3-6 h), and the yields are lower. f-Butyl chloride and adamantyl bromide have been used successfully, but the generality of the procedure needs to be demonstrated (eq 4). In contrast, acylation reactions using a wide variety of carboxylic acid chlorides have been carried out (eq 5). The initial products are protected forms of Q ,/3-diketo esters which can be isolated in yields of 72-93%. Deprotection is accomplished using MeOH/HCl. The products are vicinal tricarbonyl compounds having the usual characteristic chemical properties such as rapid formation of hydrated derivatives. The protected forms can be used directly in the synthesis of heterocycles. ... 

Adlington RM, Baldwin JE, Catterick D, Pritchard GJ (2001) The efficient, enandoselective synthesis of quinoxaline, pyrazine and 1,2,4-triazine substituted a-amino acids from vicinal tricarbonyls. J Chem Soc, Perkin Trans l(7) 668-679. doi 10.1039/B010134P... 

Fretl996 Fretz, H., Solid Phase Synthesis of Peptides Containing Novel L-Phenylalanine Derivatives Substituted with Vicinal Tricarbonyl Moieties, Tetrahedron Lett., 37 (1996) 8479-8482. 

Wasserman, H.H. and Kelly, T.A. (1989) The chemistry of vicinal tricarbonyl compounds. Short synthesis of eudistomins T, I and M. Tetrahedron Lett., 30, 7117-7120. 

Adam, W. and Patterson, W. S., High-intensity laser-jet photochemistry formation of benzocy-clobutenedione from 1,2,3-indantrione via transient targeting,/. Org. Chem., 60,7769, 1995. Netto-Ferreira, J. C., Silva, M. T., and Puget, F. P., Photochemistry of cychc vicinal tricarbonyl compounds [2-1-2]-photocycloaddition of 1,2,3-indanetrione to electron rich olefins,/. Photochem. Photobiol. A Chem., 119, 165,1998. 

Silva, M. X, Braz-Filho, R., and Netto-Ferreira, J. C., Photochemistry of cyclic vicinal tricarbonyl compounds. Photochemical reaction of 1,2,3-indanetrione with 2,3-dimethyl-2-butene hydrogen abstraction and photocycloaddition,/. Braz. Chem. Soc., 11,479, 2000. 

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