The synthesis, thermochromism, and cycloadditive properties of an O-methylenethioquinone system

Abstract

). The irradiation of 4,5-benzo-1,2-dithiole-3-thione (1) in the presence of cyclopentene and of tetramethylethylene gives 1 : 1 adducts. In solution these adducts are in equilibrium with eightmembered-ring dimers. The thermodynamic parameters for this equilibrium have been determined. The available evidence suggests a head-to-head configuration. These same monomeric adducts give Diels-Alder addition products with normal dienophiles, but also react similarly with simple thiones (adamantanethione, norbornanethione, cyclohexanethione) to give thioorthoesters. The structures of the latter substances have been demonstrated both spectroscopically and, chemically, by hydrolysis to a thiosalicylic acid derivative. The thioorthoesters have been show11 to undergo stereoisomerization on acid catalysis. Of the two mechanisms considered for this process (reversal to thiones and ion-pair formation) the former has been excluded. P. DE MAYO et H. Y. NG. Can. J. Chem. 55,3763 (1977). L'irradiation du benzo-4,5 dithiol-1,2 thione-3 (1) en presence de cyclopentene et de tetramCthyltthylene conduit a des adduits 1 :l. En solution, ces adduits sont en equilibre avec des dimeres cycliques a huit chainons. On determine les parametres thernlodynamiques pour ces Cquilibres. L'indice connue est en faveur d'une configuration ttte a ttte. Ces mtmes adduits monomeres donnent des produits d'addition Diels-Alder avec des diCnophyles normaux, mais ils rkagissent d'une maniere analogue avec des thlones simples (adamantanethione, norbornanethione, cyclohexanethione) pour conduire a des thioorthoesters. On determine la structure de ces derniers spectroscopiquement et chimiquement en les hydrolysant en derives d'acide thiosalicylique. Les thioorthoesters demontrent une tendance a la stereoisom6risation lors d'une catalyse acide. Deux mtcanismes sont envisages pour ce processus; ]'inversion en thiones et la formation d'une paire d'ions; seul le dernier est retenu.[Traduit par le journal]

Reduktion von 3‐Amino‐1,2‐benzisothiazolen und 3‐Imino‐1,2‐benzisothiazolinen zu 2‐Mercaptobenzamidinen, Benz‐amidiniumthiolaten oder 1,2‐Benzothiochinonmethiden

“…Nur bei der N,N'-Diphenylverbindung 4p, bei der wir einen Beitrag der Mercaptoform annehmen, liegt die Resonanz von C-2 bei hoherem Feld (6 = 132; s. Experimcnteller Teil). (9,CH@) 3.80 (4, 3.62 w q , w , z ) 4.28 (s, CH2E) Aus Gleichgewicht 4 j ( Z , E , R2, R3…”

The reaction of 2,1-benzisothiazoline-3-thiones with acetylenic reagents

“…In this reaction the thione l a parallels the reaction of benzo-1,2-dithiole-3-thione with dimethyl acetylenedicarboxylate (2), but there the monoadduct rapidly reacted with more acetylenic ester to form a diadduct. No such monoadduct dimers are reported from the reaction of the structurally related benzo-or naphtho-1,2-dithiole-3 -thiones with acetylenic reagents, but the photo-reaction with alkenes produces adducts which are in equilibrium with dimers (4,5). It is also reported that o-xylylenes may undergo dimerisation (6) but a more closely related imino-o-quinomethide only shows a [2 + 41 type addition (7).…”