Using the reaction between four representative vinylphosphonium salts and three a-mercaptoaldehydes, 12 3,4-unsubstituted 2,5-dihydrothiophenes (1) were prepared.The reaction proceeds in excellent yields under mild conditions. The use of these compounds in thesynthesisof dienes is indicated.On a prepare 12 dihydro-2,5 thiophenes non substitues en position 3,4; ces syntheses impliquent la reaction de quatre sels reprtsentatifs d e vinylphosphoniurn avec trois a-mercaptoaldthydes. L a reaction se produit avec d'excellents rendements d a n s des conditions douces. O n montre comment ces composes peuvent &tre utilises pour la synthese de dienes.[Traduit par le journal]Can. J . Chem..52,1934Chem..52, (1974 Recently, we have reported (1, 2) a new route to conjugated dienes (2) using 2,5-dihydrothiophenes (1) as key intermediates (Scheme 1). As we have shown, these compoi~nds are readily available from the reaction of vinylphosphonium salts and a-mercaptoketones. The synthetic advantages to this method have already been outlined (2).The dihydrothiophenes reported thus far have been derived from a-mercaptoketones and are substituted at the 3-position. As the final step in the reaction (Scheme 2) is a Wittig reaction, a process known to be dramatically subject to steric hindrance (3, 4), we had every reason to expect that employing a-mercaptoaldehydes in the reaction should afford excellent yields of 1. exist as highly insoluble dimers o r polymers (2) were more difficult to prepare than the corresponding ketones but their reactions with the representative vinylphosphonium salts were more rapid. In most cases these reactions were essentially complete in a few hours at 100" but in others a longer reaction time was required for maximum yields (Table 1). Although all reactions were run usingequimolar quantities of reactants it has been observed that a slight ( l o x ) excess of the vinyl salt increased the yields dramatically (5).As can be seen from Table 2, with the exception of compound 18, the n.m.r. absorptions for the vinyl hydrogen atoms of the dihydrothiophenes occurred as sharp singlets. The chemical shifts of these appear t o be dependent upon the degree of substitution at the 2,5-positions. We are pursuing this point. It should also be noted that the n.m.r. spectra provided no evidence for the presence of geometric isomers where these were possible. As the further conversion ofthe dihydrothiophenes to dienes occurs by a stereospecific pathway (2, 6) a highly stereoselective synthesis of compounds of type 1 would be of great importance. At present, we are engaged in a study of the reaction stereochemistry which will be reported at a later date. SCIIEME 2 ExperimentalThese expectations were realized (Table I). The Unless otherwise noted, n.m.r. spectra were obtained reactions were run as ~reviouslv described (2) salts by in situ isomerization of their allyl isomers Gas-liquid chromatography analyses were carried out on a n F and M Model 720 gas chromatograph utilizing a n when required. The a-mercaptoaldehydes whic...

The syntheses of the arylindium compounds L2InX (X = Cl, I), L2InR (R = CH3, C6H5), L3In and L2InSnPh3 (L = 2-[(dimethylamino)methyl]phenyl) are reported. The pathway of the redistribution reactions involving InCl3 and L3In are discussed. Mass and 1H nmr spectra are reported.

. The electrochemical oxidation of titanium metal in the presence of an essentially nonaqueous electrolyte phase yields titanium(II1) species in solution. It has been shown that this method of generating TiX3 (X = balancing anion) forms the basis of a convenient way of reducing it1 sit// certain organic functional groups (sulfoxide, oxime, haloketone, vinyl dicarboxylic acid, and nitro aromatics). The stoichiometry of the reaction has been established in each case, and corresponds to the oxidation of TiX3 and the formation of the appropriate organic compound. The yields are comparable to those reported in experiments using aqueous titanous chloride.OLYMPIA CHRISTOFIS, JACOB J. HABEEB, RICHARD S. STEEVENSZ et DENNIS G. TUCK. Can. J. Chem. 56,2269Chem. 56, (1978.L'oxydation electrochimique du titane sous forme metallique en presence d'une phase electrolytique essentiellement non-aqueuse conduit 2 des especes titane(ll1) en solution. On a montre que cette methode de produire du TiX3 (X = un anion) peut servir de base pour une methode convenable de reduire in situ un certain nombre de groupes fonctionnels organiques (sulphoxyde, oxime, halocetone, acide dicarboxylique vinylique et nitro-aromatique). On a etabli la stoechiometrie de la reaction dans chaque cas et elle correspond a I'oxydation d e TiX3 et a la formation du compose organique approprie. Les rendements sont comparables avec ceux rapportes dans des experiences faisant appel a du chlorure titaneux en solution aqueuse.[Traduit par le journal]

The preparation of a series of vinyltriphenylphosphonium salts, all of which bear a substituent on the carbon attached to phosphorus, is described. Yields are generally poor unless a symmetrical secondary allylic halide can be used. The use of these salts in the preparation of substituted 2,5-dihydrothiophenes has been examined. In general, reaction times are increased and product yields decreased relative to the reactions of the unsubstituted salts previously reported. This result is ascribed to steric inhibition of the intramolecular Wittig reaction.

Verschiedene Methoden zur Darstellung von α‐alkylierten Vinyltriphenylphosphonium‐Salzen werden an den Beispielen von (II) und (IV) (Methode A), (VIII) (Methode C) und (XII) (Methode D) beschrieben und untersucht.