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Die Synthese der Titelverbindungen wird nach mehreren Methoden durchgeführt.

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The Knorr reaction when conducted in an aprotic polar solvent provides a new route to oxazolidine-2-thiones.REACTION of a-amino-alcohols with carbon disulphide in basic aqueous or alcoholic media is known1 to give either an oxazolidine-2-thione or a thiazolidine-2-thione depending on the structure of the amino-alcohol.2 The route taken by the reaction in aqueous KOH in refluxing CS, is constrained by the steric requirements of the carbon bearing the hydroxygroup. Thus primary alcohols react to give thiazolidine-2thiones, whereas amino-alcohols with a sterically hindered hydroxy-group give oxazolicline-2-thione.Anlino-alcohol R1 R2 R3 R4 M.p. Yield CH20H.CH2NH2

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. J. Chem. 58,604 (1980).Variation of the conformational properties in a series of 4-R-thiazolidine-2-thiones (4-R = Me, Et, iPr, tBu, OH) and 5-Rthiazolidine-2-thiones (5-R = Me, Et, iPr, tBu) is deduced from 'H nmr (Karplus 'J, chemical shifts, 'J,,,, 'JS5,) 13C nmr data and CNDO-2 calculations. In the absence of any transannular interaction, tricinal constraints and van der Waals requirements of the substituents control the conformational equilibrium. The pseudo-axial arrangement is favoured when 4-R = Me, while the substituent presents no preferential orientation when 5-R = Me. As the size of the 5-alkyl and the 4-alkyl substituent increases, its pseudo-equatorial orientation and the predominance of the C4C5 out-of-plane half-chair conformation are favoured. This does not lead to conformational exclusivity even when 4-R or 5-R is tBu. When 4-R is hydroxy, there is a definite pseudo-axial conformation (anomeric effect) and the ring preference is of the C4 out-of-plane type.F. CHANON, M. RAJZMANN, M. CHANON, J. METZGER, C . POUZARD et T. DRAKENBERG. Can. J. Chem. 58.604(1980). Les Cvolutions conformationnelles dans les R-4 thiazolidinethiones-2 (R-4 = Me, Et, iPr, tBu, OH) et les R-5 thiazolidinethiones-2 (R-5 = Me, El, iPr, tBu) sont deduites de l'ensemble des rksultats rmn 'H ('J- Karplus,6,, 'J,,,, 2J44,), rmn "C et calculs CNDO-2. En I'absence d'interactions transannulaires, les contraintes cicinales et de van der Waals des substituants contr6lent i'equilibre conformationnel. Lorsque R-4 = Me, sa prdfkrence est Iigerement pseudo-axiale tandis que le substituant R-5 = Me n'a pas d'orientation spicifique. On observe, simultanement a une augmentation de la taille du substituant alkyle, une orientation de plus en plus equatoriale de ce dernier et une predominance accrue de la conformation demi-chaise avec C4C5 hors plan. Ceci ne conduit pas toutefois a un blocage conformationnel mCme pour le tBu. Pour R-4 = OH, une nette preference pseudo-axiale se manifeste (effet d'anomirie) et le plissement du cycle est du type enveloppe avec C4 hors du plan du thiocarbonyle. IntrodustionHaving introduced substitution at C4 (Pb, Ic, Id, In the preceding paper (1) we have shown for l e 7 I f ) and C 5 (2b, 2c, 2 d j 2e)9 i.e. thiazolidine-2-thione ( l a ) the existence of equilibrium Tal :The conformer stability increases from left to right and the C4C5 torsional angle was evaluated to be ca. (Table 2) and 'H nmr experi-ppm) and the 4-R-THTH-2 series (Aa4,, = + 1.12 mental data (Table I) Table 3. They reveal a slight pseudo-equatorial preference exhibited by the 4-methyl derivative 16 and a slight pseudo-axial one for the 5-methyl derivative 26. The orientation of R is increasingly equatorial with increasing substituent size, particularly so for 4-R or 5-R = Et and iPr. A pseudo-equatorial preference close to 100x is not observed. The effective orientation of the methyi substituent is supported by substituent effects on 13G chemical shifts due to the introduction of methyl group (Table 4). a-and P-effects are both deshield...

. Can. J . Chem. 58,599(1980 IntroductionIn this report, we will study the unsubstituted ring Conformational analysis of heterocyclic systems did not begin (1, 2) until well after the birth of classical conformational analysis (3). The uncertainty associated with the extension of well accepted tools of analysis for classical conformational systems, to unknown systems, is the main cause of this late development. For any new heterocyclic system under study, the obtained informations must be cross-checked by the use of different methods. The and in the next report (4), we will consider the effect of perturbations in this system due to the presence of substituents at positions 3, 4, and 5. This first paper tentatively answers the questions: is the heterocycle planar or puckered? If indeed the ring is puckered, to what extent is it, compared with its alicyclic homologs? Do the experimental results allow us to affirm that a pseudo-rotation process exists in this ring system? following reports illustrate this approach. The purResults and Discussion pose of this paper is to define the conformational properties of the nonsymmetric monounsaturated Obseruarion and Eualuation ofthe Degree ofpuckering heterocyclic system, namely thiazolidine-2-thione of the Thiazolidine-2-thione Ring (TH-2-33) 8.' H Nuclear Magnetic Resonance -JVi, -Application of the Simplified Karplus Equation 'Revision received November 12, 1979. he-analysis of the 'N nmr spectra (Table 1) torsional angle cp between the two corresponding vicinal carbon atoms.In the case of a planar ring in TH-2-TH: The abnormally large value for 180" (6-8) rules out the possibility of a planar conformation for the TH-ZTH ring.'N Nuclear Magnetic Resonance -JYi, -The Use of Lambert's R-ualue Method Assuming a puckered ring, thiazolidine-2-thione exists in a rapidly interconverting equilibrium mainly between two energetically equivalent conformations:The $I-CLCC5-S torsional angle cp, can be evaluated (Lambert's R-value method (9)) using the ratio of the experimental vicinal coupling constant values in the CH,-CH, fragment: i.e."tl~ere appears to be no theoretical reason to preclude applications to all common and medium rings" (9). In the TH-2-TH case, R = 0.84, i.e. cp, = 41"; therefore Lambert's R-value implies a significant puckering of the ring as in the cyclopentane (10) and dioxolane cases (1 1). 'H Nuclear Magnetic Resonance -2JHjH5, and J, , , , , Values In the series of 4-and 5-alkyl-substituted (Me, Et, iPr, tBu) TH-2-TH derivatives, the 2JH,,,r or 2J,j,j, values vary in a continuous and coherent way (4). However, substituent electronegativities vary only slightly along the series; thus the main factor which induces deviations in the J,,, values in the X-CH, fragment is the variation of the dihedral angle between the C-H bonds and the "lone-pairs orbitals" of the heteroatom x (12). The observed change in the J,,,, values in the alkylated series was therefore assigned to conformational modifications of the ring (4): that establishes the mobility of the thiazol...

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