An unambiguous and precise method for the synthesis of 3,1-benzoxathiin-4-ones/1,3-benzodioxin-4-ones by the reaction of propargylic alcohols and salicylic/thiosalicylic acids under a catalyst-free and open-air atmosphere is described.

A series of cylic diazoamides and diazoamines were synthesized. Treatment of these cylic diazoamides and diazoamines with a catalytic amount of rhodium(II) acetate furnished the corresponding cyclic enamides and enamines, respectively. Interestingly, cyclic diazoamines produced stereoselectively Z-enamines.The utility of a-diazo carbonyl compounds in modern organic synthesis and their participation in a variety of transformations like cyclopropanation, insertion reaction and ylide formation is well documented. 1 The tandem processes involving rhodium carbenoids generated from diazo carbonyl compounds with a catalytic amount of rhodium(II) acetate have been used to construct various complex polycyclic systems. 2 The rhodium(II)-catalyzed reactions of cyclic and acyclic diazo ketoamides were skillfully applied to generate ylides followed by trapping with dipolarophiles to synthesize various alkaloids 3 and nitrogen containing heterocycles. 2,4 The study of b-hydride elimination reactions of rhodium carbenoid is scarcely reported in the literature, particularly to obtain cis-enoates, 5 trans-b-methoxy enones 6 and a,b-unsaturated esters. 7 However, to the best of our knowledge there is no report dealing with the b-hydride elimination chemistry of diazoamides and diazoamines. 1 In continuation of our interest on the reactions of diazo carbonyl compounds 8 and to expose the novel utilities of these diazo compounds, we herein wish to report the results of bhydride elimination reactions of cyclic diazoamides and diazoamines in the presence of rhodium(II) acetate as a catalyst.For this purpose, a-diazo carbonyl compounds 4a-f having b-hydrogen atoms were chosen for this study. The required cyclic diazoamides 4a-c can be easily prepared from the corresponding cyclic amides 1a-c as described below. The Michael addition reaction 9 of cyclic amides 1a-c and ethyl acrylate afforded the corresponding cyclic amides 2a-c in quantitative yields. To generate a diazo group adjacent to ester functionality, the formylation 10 reaction of cyclic amides 2a-c using sodium hydride/ethyl formate was carried out. The formylation took place smoothly only a to the ester functional group and provided compounds 3. Without the isolation of formyl compounds 3, the diazo transfer reaction was performed using mesyl azide to afford the cyclic diazoamides 4a-c in good yields (Scheme 1).We initially investigated the performance of diazoamide 4a using rhodium(II) acetate as a catalyst in the absence of any dipolarophile. Diazoamide 4a was dissolved in anhydrous benzene and refluxed with 0.3 mol% of rhodium(II) acetate for 25 h. The reaction was followed by TLC until the disappearance of diazoamide 4a. The chromatographic purification of the crude reaction mixture afforded two products which were characterized as cyclic enamides of type 5a (40%) and 6a (31%) with Z and E geometry, respectively (Scheme 1, Table). Scheme 1IR spectrum of compound 5a showed a band at 1632 cm -1 indicating the presence of a olefin functional group. The 1 H NMR spectrum of ...

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2005 C-C bond formation O 0282Imidazolium Salts as Phase-Transfer Catalysts for the Dialkylation and Cycloalkylation of Active Methylene Compounds. -The dialkylation/cycloalkylation of active methylene compounds (I) is efficiently promoted by catalytic amounts of imidazolium-type ionic liquids as phase transfer catalyst. Reaction with 1,3-dibromopropane gives the mono-alkylated bromides (XI) instead of the expected cyclobutanes. With an excess of active methylene compounds, the bis-alkylated products (XII) are obtained. -(MUTHUSAMY*, S.; GNANAPRAKASAM, B.; Tetrahedron Lett. 46 (2005) 4, 635-638; Cent. Salt Mar. Chem. Res. Inst., Bhavnagar 364 002, India; Eng.) -Mais 20-045

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