Sulphides epoxy

A new synthetic approach to the synthesis of germacrane sesquiterpenoids involving cyclization of 10,ll-epoxy-rran5,trans-farnesyl phenyl sulphide (306) provides a mixture of hedycaryol (307) and the isomeric alcohols (308) and (309). Studies on the biosynthesis of germacrane sesquiterpenoids have appeared recently. 

The low molecular weight poly sulphides have found somewhat greater use. Of general structure HS—R—SH and with molecular weights of approximately 1000 they will react with the epoxy group to cause chain extension but not cross-linking. The normal hardeners must therefore be employed in the usual amounts... 

Under Payne rearrangement conditions, sodium Z-butylthiolate provides 1-Z-butylthio-2,3-diols with very high regioselectivity. However, the selectivity is affected by many factors, including reaction temperature, base concentration, and the rate of addition of the thiol. These sulphides can then be converted to the l,2-epoxy-3-alcohols, which in turn react with a wide variety of nucleophiles specifically at the 1-position (Scheme 4), This methodology circumvents the problems associated with the instability of many nucleophiles under Payne conditions [731,... 

The formation of rearranged products during nucleophilic substitution in a-bromo-ketones probably involves enolisation, followed by allylic (5n2 ) substitution. The ready conversion of4, 5i8-epoxy-3-ketones (45) into 2a-acetoxy-or 2a-hydroxy-4-en-3-ones is similarly rationalised.When the nucleophile is dimethyl sulphoxide, the resulting 2-oxysulphonium ion (46) breaks down with elimination of dimethyl sulphide to give the 4-ene-2,3-dione (47), or its A -enolic equivalent (48). 

A comprehensive study of the thermal degradation of epoxy resins has been reported by Lee [239]. Their stability was found to be lower than that of polycarbonate, polyphenylene sulphide and teflon (Fig. 64). 

Allylic alcohols (12) are formed when a,8-epoxy sulphides are treated with 3-5 equivalents of BuLi at -70°C (Scheme 17).40 Interestingly, clean desulphurisation to give the epoxide product (13) was also possible by the use of less BuLi at -100°C. 

In the preparation of various unsaturated amides, the dianion of -phenyl-2-(phenyIsulphonylmethyl)propenamide (49) proved to be a versatile synthon. Borohydride reduction of alkylation products of the dianion occurred in high yield to afford moderate overall yields of ,B-unsaturated amides.The dianion of the corresponding phenyl sulphide alkylated poorly giving small amounts of oth a- and y-alkylation products, whereas the sulphone-ester corresponding to (49) was found to be labile under the deprotonation conditions. Compound (49) was also employed in the development of a general strategy for the synthesis of 3,4-epoxy-2-methylene-alkanoic acid amides (Scheme 29). ... 

Epoxy sulphides convert to 3-trimethylsiloxy-l,2-thiiranium salts which with nitrogen nucleophiles give 1-substituted 3-hydroxy 2-thioether and siloxycyclopnq)anesareintraniediate in cyclohexenone synthesis, while siloxycyclobutanecarboxylic esters ring open with RCHO to... 

Epoxy alcohols are the normal products of the [VO(acac)2]+(Me2C(CN)N a -catalysed oxidation of cyclic olefins by dioxygen however, cyclo-octene is oxidized exclusively to cyclo-octene oxide. The oxidation of sulphides and alkenes by peroxides with a [V(0)(acac)2] catalyst have been compared and the nature of the monoperoxovanadium(v) intermediate investigated. Complexation of a Cr(CO)3 unit to aromatic hydrocarbons enhances the benzylic positions towards attack by superoxide ion, e.g., diphenylmethane is readily converted into benzophenone. Metal porphyrin complexes ML4 continue to attract attention both as reversible oxygen-carriers (M = Fe) and oxidation catalysts (M = Mn, Fe, or Co ). For example [Mn (=0 IPh)(TPP)Cl] is believed to be involved in the oxidation of cyclohexene to cyclohexanol by PhIO in the presence of [Mn(TPP)]+ and a ferryl intermediate [Fe (0)L4] has been proposed in the oxygenation of triphenylphosphine with iron(ii) porphyrin. [M(TPP)]X (M=Mn, X = OAc M=Fe, X=C1 M = Co, X=Br) catalyses the epoxidation of styrene and cyclohexene with NaOCl under phase-transfer conditions. ... 

Rautenstrauch has shown that the cyclobutane ring system found in the monoterpenes fragranol and grandisol can be produced by intramolecular cyclization from an epoxy-sulphide of the type (43), and Corbel et al have demonstrated the use of epoxy-sulphones [viz. (44)] in the elaboration of cyclobutanols. 

Azodicarboxylate esters give a-substitution products with aliphatic sulphides [e.g. R SCHjR gives R SCHR N(C02Et)NHC02Et] " u.v.-irradia-tion improves yields. Chloromethyl p-tolyl sulphide gives a -epoxy-sulphides (cis-trans mixtures) with aldehydes, catalysed by DABCO, thus completing the series a(3-epoxy-sulphide, sulphoxide, sulphone. 

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