The Wittig reaction of quinisatines (1a,b) with 1‐ethoxycarbonylethyliden‐ (2a) and ethoxycarbonylmeth‐ylenetriphenylphosphorane (2b) has been investigated. In both cases unusual reaction products (3a,b and 12a,b respectively) were isolated in high yields and converted to potential antiinflammatory acids 6, 8, 15 and lactones 4, 7.

The synthesis of several 2,4-diketo carboxylic acids by standard methods was undertaken to study the substrate speciÐcity of the carbon-carbon bond hydrolases. It was shown by 1Hand 13C-NMR experiments that compounds with 4-alkyl, 4-alkenyl and 4-alicyclic substituents exist in three main forms : 2,4-diketo, 2-enol-4-keto and 2-hydrate-4-keto. The equilibrium ratios of these aqueous solution structures were similar, but were markedly a †ected by the pH values (1.5È10.5). At pH 7.5 the ratio of these structures was approximately 4 : 5 : 1, but at low pH values the 2-hydrate predominated (B50%) and at high pH values the 2-enolate carboxylate was dominant (B80%) while the 2-hydrate was not detected. 4-Aryl substituents gave one pH-independent isomer formulated with C-2, C-3 and C-4 electrons delocalized in conjugation with the arene at C-4. This interpretation of a very rapid equilibrium between 2-and 4-enolate isomers to give a p-delocalized six-membered ring in conjugation with arene substituents is supported by the e †ect of divalent metal ions on the structural forms. Rate and equilibrium constants for several of these solution interconversions are inÑuenced by pH. Mg2`coordinates to the 2-enolate dianion of alkyl analogues, whereas Cu2`forms a six-membered p-delocalized ring with the 2-and 4-oxo atoms in conjugation with the arenes. Exchange of 2H from solvent occurs with the protons at C-3. The 2H 2 O-enriched dimers of the 4-alkyl analogues in aqua were characterized as a product of self-aldol condensations. These data have facilitated enzyme mechanism studies of CwC bond hydrolysases (b-ketolases).

Although it has been known for nearly 70 years, carbon suboxide was used almost exclusively for the preparation of simple malonic acid derivatives until about 1960. Since then, however, the significance of this unusual "bisketene" has steadily increased in synthetic chemistry (especially that of heterocyclic compounds). This progress report surveys the possible applications of C 3 0 2 in preparative organic chemistry, including photochemical reactions.Angew. Chem. internat. E d i t / Val. 13 (1974) No. 8

The use of malonates such as diethyl malonates 9, (chlorocarbonyl)ketenes 15 and bis(2,4,6-trichlorophenyl) malonates 18 as reagents for cyclocondensation with 1,3-dinucleophiles to give six-membered heterocycles is described. Further attempts to use malonates such as bis(trimethylsilyl) malonates 19 and bis(carbamimidoyl) malonates 29 as new cyclocondensation agents are described .

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The reaction of methanetricarboxylates 2a,b with indoline as well as 1,2,3,4‐tetrahydroquinoline yields tricyclic 4‐hydroxy‐2(1H)‐quinolones with an ester group in position 3 (3, 8a,b). These heterocyclic esters condense with primary aliphatic, aromatic, and heteroaromatic amines to give the corresponding amides 5a‐e and 10a‐t.

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