Chemoselectivity of the Reactions of Diazomethanes with 5‐Benzylidene‐3‐phenylrhodanine |
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Authors: | Martin S. Seyfried Anthony Linden Grzegorz Mlostoń Heinz Heimgartner |
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Affiliation: | 1. Organisch‐Chemisches Institut der Universit?t Zürich, Winterthurerstrasse 190, CH‐8057 Zürich, (phone: +41‐44‐635?4282;2. fax: +41‐44‐635?6812);3. Part of the diploma thesis of M.?S.?S., Universit?t Zürich, 2005.;4. University of ?ód?, Department of Organic and Applied Chemistry, Narutowicza 68, PL‐90‐136 ?ód? |
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Abstract: | The reactions of 5‐benzylidene‐3‐phenylrhodanine ( 2 ; rhodanine=2‐thioxo‐1,3‐thiazolidin‐4‐one) with diazomethane ( 7a ) and phenyldiazomethane ( 7b ) occurred chemoselectively at the exocyclic C?C bond to give the spirocyclopropane derivatives 9 and, in the case of 7a , also the C‐methylated products 8 (Scheme 1). In contrast, diphenyldiazomethane ( 7c ) reacted exclusively with the C?S group leading to the 2‐(diphenylmethylidene)‐1,3‐thiazolidine 11 via [2+3] cycloaddition and a ‘two‐fold extrusion reaction’. Treatment of 8 or 9b with an excess of 7a in refluxing CH2Cl2 and in THF at room temperature in the presence of [Rh2(OAc)4], respectively, led to the 1,3‐thiazolidine‐2,4‐diones 15 and 20 , respectively, i.e., the products of the hydrolysis of the intermediate thiocarbonyl ylide. On the other hand, the reactions with 7b and 7c in boiling toluene yielded the corresponding 2‐methylidene derivatives 16, 21a , and 21b . Finally, the reaction of 11 with 7a occurred exclusively at the electron‐poor C?C bond, which is conjugated with the C?O group. In addition to the spirocyclopropane 23 , the C‐methylated 22 was formed as a minor product. The structures of the products (Z)‐ 8, 9a, 9b, 11 , and 23 were established by X‐ray crystallography. |
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Keywords: | Cycloadditions Diazomethanes Ylides Rhodanine, 5‐benzylidene‐3‐phenyl‐ Thiocarbonyl ylide 1,3‐Thiazolidin‐4‐one, 2‐thioxo‐ |
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