New reaction of trithioorthoacetates. Reaction with acylating reagents

Abstract

by preparing and chromatographing samples of the dinitrophenylhydrazones. Fractional crystallization of the crude mixture of 2,4-dinitrophenylhydrazones from ethanol gave a sample (mp 131-132°) which did not depress the melting point of a known sample of cyclopropylacetaldehyde 2,4-dinitrophenylhydrazone.Cyclopropyloxirane (3). Cyclopropanecarboxaldehyde, 7.0 g (0.10 mol), was stirred under nitrogen with 28.6 g (0.14 mol) of trimethylsulfonium iodide in 60 ml of dimethyl sulfoxide. A solution of 14.0 g of potassium iert-butoxide in 150 ml of dimethyl sulfoxide was added dropwise with stirring during 30 min while cooling. After stirring for an additional 15 min, 300 ml of water was added slowly while cooling with ice. The solution was extracted with ether (3 X 500 ml) and the extract was washed with water and dried over molecular sieves. Distillation on a Teflon spinning band column gave, after removal of ether and tertbutyl alcohol, 2.6 g of 3: bp 85-90°(lit.12b bp 100°); NMR (neat) 5 0.1-0.4 (m, 4 H, cyclopropyl CHa), 0.5-0.8 (m, 1 H, cyclopropyl CH), 2.4-2.7 (m, 2 H, ox-

An unexpected synthesis of 3,5-diaryl-1,2,4-thiadiazoles from thiobenzamides and methyl bromocyanoacetate

“…11 Other more complicated methods are also reported: from the corresponding oxathiazolone, 12 benzenecarboximidamide and diethyl azodicarboxylate, 13 or from 1,2,4-oxathiazoles and Lewis acid. 14 Thermal cycloreversion of 6 H -1,3,5-oxathiazine S -oxides followed by ring closure of the resulting intermediates is also reported to yield 1,2,4-thiadiazoles.…”

Preparation of α,β-Unsaturated Ketones Bearing a Trifluoromethyl Group and Their Application in Organic Synthesis

“…Trifluoroacetylation of trithioorthoacetates results in the acylated ketene thioacetals in high yield (Scheme 4) [25]. The products seem to result from trifluoroacylation of ketene dithioacetals formed by elimination of thiols from trithioorthoacetates.…”

“…Hetero-Diels-Alder reaction with vinyl ethers leads to the corresponding dihydro-2H-pyrans in good yield (Scheme 56) [99]. The same reaction proceeds readily with β,β-bis(trifluoroacetyl)vinyl ethers and various electron rich alkenes under very mild conditions to provide functionalized 5-trifluoroacetyl-6-trifluoromethyl-3,4-dihydro-2H-pyrans in excellent yields (Scheme 57) [25]. β,β-Bis(trifluoroacetyl)vinyl alkyl ethers are much more active dienes than the corresponding β-monotrifluoroacetylvinyl ethers for which vigorous reaction conditions (80 °C, 30h) are required for cycloaddition.…”

Aplicação de α-oxoceteno ditiocetais em síntese orgânica

“…Hojo e Masuda, 4 em 1975, realizaram a síntese dos tri-haloα-oxoceteno ditioacetais 3 com reações envolvendo o uso de anidrido tri-haloacético (X = F, Cl), piridina e tio-ortoacetato de triarila 1 em uma proporção 2:2:1, éter ou clorofórmio e tempo reacional de 24 h (Esquema 2). Segundo os autores, a formação do intermediário 2 possibilita formação dos produtos, através do ataque nucleofílico ao reagente acilante.…”