Pyramidal Inversion in Cyclic Sulfonium Salts

Abstract

1499Partie experimentale. -1. Produits de dkpart: La diamine A (n = Z), Tic!, ainsi que les solvants utilids sont des produits du commerce (Fluka). 11s ont Bt6 s6chBs suivant les mBthodes habitqelles et distill& avant l'emploi. Les autres amines ont 6t6 pr6par6es d'aprhs [13] (diamine A, n = l ) , [14] (diamine A, n = 3), et [15] (diamine A, n = 4, triamines B, n = 2 e t n = 3). Prdparation des com+lexes:A une quantite connue de TiCl,, dissous d a m 20 ml de soIvant anhydre (benzhe pour les diamines et heptane pour les triamines), on ajoute goutte B goutte en 40 5 60 min. l 5-10" la quantit6, indiquke dans le tableau, d'amine dissoute dans le mbme solvant. Un pr6cipitC se forme immddiatement. Aprits 10 minutes d'agitation, on laisse reposer une nuit iL 5" La filtration, le lavage par le meme solvant et le sCchage sous vide sont effectuBs dans une bolte B gants sous azote et B l'abri de l'humiditd. 3. Mdthodes analytiques: Titane et chlore: voir [16]. Amines: dosage par acidimbtrie aprits hydrolyse alcaline et extraction B l'6ther. 4. Spectres I R . : enregistr6s l l'aide d'un spectrophotomittre Perkin-Elmer, moditle 521. Les spectres des ligands ont BtB dBtermin6s sur des films capillaires ou de 0,025 mm d'dpaisseur (fenetre de KBr ou CsBr); les spectres des complexes, en pastille de KBr (concentration: 0,5-1%). BIBLIOGRAPHIE [l] V I I P communication: A .Summary. 5and 6-membered cyclic sulfonium salts carrying methyl substituents on the ring have been synthetized and partially resolved. These salts undergo thermal stereomutation a t rates which are 108 times lower than that of non-cyclic sulfonium cations. Very stringent evidence is presented that racemisation or, where the case may be, epimerisation takes place by pyramidal inversion of the sulfur atom.

Stereomutation of cyclic sulfonium and selenonium compounds 1

“…The stereomutation rate of 4 in [ 2 H 7 ]DMF is in the order of magnitude of a literature-known thianium compound 14 and is smaller than that of 1 in D 2 O. The latter can be interpreted by the increased strain of the 6-membered ring compared to the 5-membered during the planar transition state necessary for the pyramidal inversion mechanism.…”

Nucleophilic substitution at tricoordinate sulfur(IV). Stereochemistry of dialkylarysulfonium salt formation from alkyl aryl sulfoxides

“…Journal of the American Chemical Society / 96:26 / December When 12, derived from 98% optically pure 13, was stirred with magnesium methoxide for 1.5 hr at room temperature and then hydrolyzed with 1% aqueous sodium hydroxide, a hydrolysis which normally converts alkoxysulfonium salts into sulfoxides with 90 to 100% inversion of configuration at sulfur,17 a quantitative yield of 13 was obtained but with 59% inversion. No methyl p-tolyl sulfide (14) was observed. The methoxide ion may attack the methoxy carbon of 12, the sulfur atom, or the proton a to sulfur.…”

“…20 g of sodium bromide and then extracted with four 25-ml portions of methylene chloride. The methylene chloride extract was dried over magnesium sulfate, concentrated on the rotary evaporator, and dried in vacuo yielding 0.18 g (46%) of methyl p-tolyl sulfide (14) and 0.15 g (33%) of (7? )-(+)-methyl p-tolyl sulfoxide (13); [tr]22D 25.3°( c 1, acetone), 18.0% optically pure.…”

Synthesis, stereostructure, pyramidal inversion, and alkylation of 1-thioniabicyclo[4.4.0]decane salts

“…The calculated rate at 100 °C, 4.6 X 10-5 s-1, compares well with that obtained by Fava, 8.1 X 10-5 s-1, for equilibration of 1,3,3-trimethylthianium perchlorate. 15 The AG°for the equilibrium lb^la is -0.64 kcal mol-1 at 110 °C. For comparison, ira/w-decalin is 2.7 kcal mol-1 more stable than c/s-decalm in the range 268-378 °C.…”