New Studies on [2+3] Cycloadditions of Thermally Generated N‐Isopropyl‐ and N‐(4‐Methoxyphenyl)‐Substituted Azomethine Ylides

Abstract

The thermal reaction of 1-substituted 2,3-diphenylaziridines 2 with thiobenzophenone (6a) and 9H-fluorene-9-thione (6b) led to the corresponding 1,3-thiazolidines (Scheme 2). Whereas the cis-disubstituted aziridines and 6a yielded only trans-2,4,5,5-tetraphenyl-1,3-thiazolidines of type 7, the analogous reaction with 6b gave a mixture of trans-and cis-2,4-diphenyl-1,3-thiazolidines 7 and 8. During chromatography on SiO 2 , the trans-configured spiro[9H-fluorene-9,5'-[1,3]thiazolidines] 7c and 7d isomerized to the cis-isomers. The substituent at N(1) of the aziridine influences the reaction rate significantly, i.e., the more sterically demanding the substituent the slower the reaction. The reaction of cis-2,3-diphenylaziridines 2 with dimethyl azodicarboxylate (9) and dimethyl acetylenedicarboxylate (11) gave the trans-cycloadducts 10 and 12, respectively (Schemes 3 and 4). In the latter case, a partial dehydrogenation led to the corresponding pyrroles. Two stereoisomeric cycloadducts, 15 and 16, with a trans-relationship of the Ph groups were obtained from the reaction with dimethyl fumarate (14; Scheme 5); with dimethyl maleate (17), the expected cycloadduct 18 together with the 2,3-dihydropyrrole 19 was obtained (Scheme 6). The structures of the cycloadducts 7b, 8a, 15b, and 16b were established by X-ray crystallography.

Thermal [2+3]‐Cycloadditions of trans‐1‐Methyl‐2,3‐diphenylaziridine with CS and CC Dipolarophiles: An Unexpected Course with Dimethyl Dicyanofumarate

“…In our earlier reports, reactions of N-substituted aziridines with acetylenes [10], alkenes [10] [11], carbonyl [11] [12], and thiocarbonyl groups [10] [13 -15] were described. All of the reported reactions yielded [2 þ 3]-cycloadducts with the expected configuration, i.e., cis-2,3-disubstituted aziridines led to trans-disubstituted products, and trans-2,3-disubstituted aziridines gave cis-disubstituted cycloadducts.…”

“…In our earlier publication, the reaction of cis-1-isopropyl-2,3-diphenylaziridine with 5 in refluxing toluene was described to give a mixture of the corresponding trans-2,5-dihydropyrrole-3,4-dicarboxylate and the aromatized pyrrole derivative in a 85 : 15 ratio [10]. In the present study, a 1 : 1 mixture of cis-1a and 5 in toluene was heated to reflux for 10 h, and the progress of the reaction was monitored by 1 H-NMR spectroscopy, which indicated that only one product was formed.…”

Synthesis and Reactions of a New Cyclobutanethione Derivative

“…[22][23][24]). Thermolysis of cis-1-methyl-2,3-diphenylaziridine (22) in boiling toluene in the presence of 4b afforded a single product whose structure was again established by X-ray crystallography [25] (Scheme 7). In accordance with the expected reaction course, the Ph groups are trans oriented, i.e., the intermediate 1,3-dipole 23 has been generated by a conrotatory ring opening of 22.…”

Crystal Structure of Two Dimethyl 1,3-Thiazolidinedicarboxylates Obtained in Thermal [2 + 3]Cycloaddition of an Azomethine Ylide with 2,2,4,4-Tetramethyl-3-Thioxocyclobutanone

“…In a series of our recent papers these 1,3-dipoles were shown to add smoothly to some cycloaliphatic and aromatic thioketones to yield in a one-step procedure functionalised 1,3-thiazolidines [2]. In all cases formation of 5-membered ring occur under stereochemical control which is governed by orbital symmetry rules [3]; however, in some instances secondary processes were observed which led to isolation of stereoisomers which do not fulfil these rules [2]. Moreover, in the case of nonsymmetrical azomethine ylides, regiochemical problem and spectroscopic methods are with only limited importance to solve the true structure of isolated cycloadduct.…”

“…1 Department of Crystallography and Crystal Chemistry, University of L ódź, Pomorska 149/153, PL-90236 L ódź, Poland. 2 Section of Heteroorganic Compounds, University of L ódź, Narutowicza 68, PL-90136 L ódź, Poland. 3 To whom all correspondence should be addressed: e-mail: reczek@ uni.lodz.pl…”