The cyclic trithiocarbonates 1,3-dithioIane-2-thione (4) and 1,3-dithiole-2-thione (9) in 1,2-dichloroethane and MeCN, respectively, react with alkyl-and phenyl-substituted oxiranes 2 in the presence of Lewis acids to give l-oxa-4,6,9-trithiaspiro[4.4]nonanes 5 and 6 (Scheme 2) and l-oxa-4,6,9-trithiaspiro[4.4]non-7-enes 10 and 11 (Scheme 3 ) . respectively. The reactions proceed regioselectively yielding 2-alky1(5,10) and 3-phenyl derivatives (6, 11) as the main products. From the reaction of 4 and 2-phenyloxirane (2e) with TiCl,, 2-phenyl-l,4,6,9-tetrathiaspiro[4,4]nonane (7) is isolated as a minor product. The molecular structures of Sa, 6e, and 7 are established by X-ray crystallography.1. Einleitung. ~ Vor kurzem haben wir iiber eine neue 1,3-Oxathiolan-Synthese berichtet [ 11. Dabei werden aus 1,3-Thiazol-S(4H)-thionen 1 und Oxiranen 2 unter BF,-Katalyse spirocyclische 1,3-Oxathiolane vom Typ 3 gebildet (Schema I ). Die Reaktion verlauft mit alkyl-substituierten Oxiranen (R = Alkyl) regio-und stereoselektiv zu 2-Alkyl-Derivaten, bei denen R trans zum disubstituierten C(9) orientiert ist. Mit Phenyloxiran (2; R = Ph) entsteht dagegen ein cisltrans-Gemisch des entsprechenden 3-Phenyll-oxa-4,6-dithia-8-azaspiro[4.4]non-7-ens. In beiden Fallen wird der Oxiran-Ring unter Spaltung einer C,O-Bindung geoffnet, das 1,3-0xathiolan also aus den Segmenten C-S und 0-C-C aufgebaut.

The 1,3-dipolar cycloaddition of cyanonitrile oxide to 2,3- and 2,5-dihydrofurane, 7-oxabicyclo[2,2,1]-2-heptene and derivatives of 1,3-dioxep-5-ene is described. The condensed isoxazolines Ia, IIIa, Va, Vc, Vd thus prepared are rearranged on irradiation into cyanosubstituted heterocyclic enaminoaldehydes IIa, IVa, VIa, VIc. The quantum yields of the photorearrangement of cyanoderivatives are higher than those of the phenyl derivatives, being within the limits from 0·068 to 0·19. The reaction of II with hydrazine gives the derivative IX of oxazino[4,5-d]pyridazine.

The dependence has been found of the quantum yield Φ of photochemical rearrangement of the title compounds (where R means ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, 2-furyl, 2-thienyl) on the exo(I) or endo (II) arrangement of the R substituent. The endo derivatives exhibit higher Φ values (0.020-0.041) than the exo derivatives (0.007-0.019). The photochemical rearrangement gives the derivatives of 2-R-6-phenyl-7-formyl-2,4,5,8-tetrahydro-1,3-dioxa-5-azocine as the single products in good yields. The 2-furyl derivative gives polymeric products. The title compounds have been prepared by 1,3-dipolar cycloaddition of benzenenitriloxide to the respective substituted 1,3-dioxep-5-enes.

An unexpected contraction of the 8-membered ring to a 6-membered one occurring when 6-aryl-7-formyl-2,4,5,8-tetrahydro-1,3-dioxa-5-azocines II were treated with tert-butylamine afforded 4-aryl-5-formyl-1-(1,1-dimethylethyl)-1,2,3,6-tetrahydropyrimidines III. Reaction conditions for the photorearrangement of chlorophenyl-substituted condensed isoxazolines I to II were worked out. The reaction sequence: 1,3-dipolar cycloaddition, photochemical rearrangement, treatment with tert-butylamine constitutes a new route to pyrimidine derivatives from 2H,4H,7H-1,3-dioxepine.

3-R-Alkoxycarbonyl-5-formyl-2,3-dihydro-6H-1,3-oxazines IIa-IIc (R = methyl, ethyl, isopropyl) as primary photoproducts formed by a rearrangement of 3-R-alkoxycarbonyl-3a,4,6,6a-tetrahydrofuro[3,4-d]isoxazoles Ia-Ic undergo cyclization to bicyclic lactones IIIa-IIIc due to further irradiation. The photochemical transformation of compounds II into III constitutes a new kind of photo-induced rearrangement. The quantum yields are very little dependent on the presence of oxygen and polarity of the solvent. The proposed concerted mechanism of the photorearrangement is discussed.