1,3‐Dipolare Cycloadditionen eines Carbonyl‐ylids mit 1,3‐Thiazol‐5(4H)‐thionen und Thioketonen

Abstract

In p-xylene at 1 50°, 3-phenyloxirane-2,2-dicarbonitrile (4b) and 2-phenyl-3-thia-l-azaspiro[4.4]non-l-ene-4thione (la) gave the three 1 : 1 adducts trans-3a, cis-3a, and 13a in 61, 21, and 3 YO yield, respectively (Scheme 3). The stereoisomers trans-3a and cis3a are the products of a regioselective 1,3-dipolar cycloaddition of carbonylylide 2b, generated thermally by an electrocyclic ring opening of 4b (Scheme6), and the C=S group of la. Surprisingly, 13a proved not to be a regioisomeric cycloadduct of l a and 2h, but an isomer formed via cleavage of the 0-C(3) bond of the oxirane 4b. A reaction mechanism rationalizing the formation of 13a is proposed in Scheme 6. Analogous results were obtained from the reaction of 4b and 4,4-dimethyl-2-phenyI-1 ,3-thiazole-5 ( 415' )thione (lb, Scheme 3). The thermolysis of 4b in p-xylene at 130" in the presence of adamantane-thione (10) led to two isomeric 1 : 1 adducts 15 and 16 in a ratio of ca. 2: 1, however, in low yield (Scheme 4). Most likely the products are again formed via the two competing reaction mechanisms depicted in Scheme 6. The analogous reactions of 4b with 2,2,4,4-tetrainethyIcyclobutane-l,3-thione (1 1) and 9H-xanthene-9-thione (12) yielded a single 1 : 1 adduct in each case (Scheme5). In the former case, spirocyclic 1,3-oxathiolane 17, the product of the 1,3-dipolar cycloaddition with 2a corresponding to 3a, was isolated in only 11 % yield. It is remarkable that no 2:l adduct was formed even in the presence of an excess of 4b. In contrast, 4b and 12 reacted smoothly to give 18 in 81 % yield; no cycloadduct of the carbonyl-ylide 2a could be detected. The structures of cis-3a, 13a, 15, and 18, as well as the structure of 14, which is a derivative of rrans-3a, have been established by X-ray crystallography (Figs. 1-3 , Table).

Chemoselectivity of the Reactions of Diazomethanes with 5‐Benzylidene‐3‐phenylrhodanine

“…1) as dipolarophiles. All reactions with nitrile imines [12], nitrile ylides [12] [13], thiocarbonyl ylides [14], carbonyl ylides [15], azomethine ylides [16], and diazo compounds [17] occurred at the C¼S bond leading to spirocyclic products. Similarly, organic azides and benzonitrile oxide underwent a cycloaddition with the C¼S bond of 1, but the initially formed spirocyclic products were not stable, and the corresponding 1,3-thiazol-5(4H)-imines [18] and 1,3-thiazol-5(4H)-one [19], respectively, were obtained.…”

Experimental and theoretical study of the [3 + 2] cycloaddition of carbonyl ylides with alkynes

“…Among them, [3 + 2] cycloaddition (32CA) reactions, also named 1,3-dipolar cycloadditions, whose general concept was introduced by Huisgen and co-workers in 1960s, 1 are versatile tools for building five-membered heterocycles, and current understanding of the underlying principles in these reactions has grown from a fruitful interplay between theory and experiment. 2 Carbonyl ylides, generated by thermal ring opening of epoxides, are known to react with π-bonds of alkynes, 3 alkenes, 3a,b,4 imines, 5 aldehydes 5c,6 and ketones, 7 and thioketones, 8 affording highly substituted dihydrofurans, tetrahydrofurans, oxazolidines, dioxolanes, and oxathiolanes, respectively. Following recent studies of the 32CA reactions between, on the one hand, carbonyl ylides and, on the other hand, aldehydes, 5c imines, 5c and ketones, 7 in which we have performed theoretical calculations using density functional theory (DFT) methods to depict the mechanism of these reactions, we here report our studies concerning the reactions involving unsymmetrical alkynes.…”

Dispiro[fluorene-9,5′-[1,2,3,4]tetrathiane-6′,9′′-fluorene]

“…The focus of our studies is on 1,3-dipolar cycloadditions which lead to new sulfur heterocycles. Among the 1,3-dipoles that have been used are nitrile ylides (Bu È chel et al, 1984), nitrile imines (Linden et al, 1999), azides (Mloston & Heimgartner, 1995;Mloston et al, 1996), diazo compounds (Ka È gi et al, 1996;Kelmendi et al, 2000), carbonyl ylides (Meier et al, 1997) and thiocarbonyl ylides . In some cases, such as with azides and diazo compounds under forced conditions, elemental sulfur was formed (`twofold extrusion'; Guziec & San®lippo, 1988), which led to the formation of products containing more than one S atom per molecule.…”