Substituted epoxides

Several alioyclio epoxides substituted with polar atoms have been reduced with lithium aluminum hydride, largely by Moueesron and eo-workers, although subsequent investigators3 -1,70 have expressed disagreement with certain of their results. Experimental difficulties in... 

Scheme4.65. Regioselective reductive ring opening of epoxides substituted with electron-withdrawing groups [275-279],...

Epoxides substituted with oxymethyl or other electron-withdrawing groups are usually attacked by cyanide in the presence of acids at the carbon which can form the better stabilized carbocation (Scheme 4.88). As with other nucleophiles, for 2,3-epoxypropanols this regioselectivity can be reversed by addition of boron-derived Lewis acids (first example, Scheme 4.88). 

The current product range of developmental samples covers monofunctional fluids of aminoalkyl, chloroalkyl, vinyl, and (meth)acryloyl types. Molecular mass is 1700 and 4000 Da, and product viscosities reach from 15 to about 80 mPas. The appearance of the fluids is optically clear and colorless to slightly amber. Technologically accessible future fimctionalities include caibinol, epoxide, substituted phenyl, hydrosilyl, caiboxy, sulfhydtyl, polyglycol, and other groups (see literature attached). In Fig. 2, currently available products are sketched. 

The carbon atoms in cyclic sulfates and sulfites are highly reactive towards nucleophilic reagents [50], which allows us to use such functionalities as the epoxide substitutes in many reactions. The 3,5-sulfites having the neighboring free hydroxyl group were used for preparation of anhydronucleosides. Thus, D-xy/o-furanoside nucleoside 66 reacted with SOCI2 in p)Tidine to afford the cyclic sulfite 67, which upon treatment with sodium bicarbonate furnished the 2,3-anhydro-nucleoside 68 (O Scheme 21). 

Excellent heat and mass transfer characteristics of the SDR have been confirmed by the study of a phase-transfer-catalyzed Darzens reaction for preparing a drug intermediate. The SDR allowed for a 99.9% reduction in reaction time, 99% reduction of inventory and 93% reduction in the level of impurities [106]. Other possible applications of the SDR include polymerizations and polycondensations (in both cases considerable time savings and more uniform product) as well as precipitation/crystallization (smaller crystals with much narrower size distribution). Two large chemical companies have patented processes based on spinning-disc technology. SmithKline Beecham has claimed a method to epoxidize substituted... 

Recently Flisak et al. [7] achieved an extension of this reaction — using commercially available poly (L)-leueine they succeeded in epoxidizing substituted chalkones with high enantioselectivity according to this method. The polymer catalyst can be recovered without any loss of activity and can be used for further asymmetric epoxidations. 

Reductive cyclization. Epoxides substituted with a carbon chain terminated (at a proper length) in an allenyl group are converted into cyclic products containing vicinal hydroxymethyl and vinyl substituents. 

Reduction of epoxides. Epoxides substituted by aryl groups are reduced by this ate complex of 9-BBN at the more substituted carbon atom, whereas aliphatic epoxides are reduced less readily and at the less hindered position. The behavior of (1) generally differs from that of complex metal hydrides. 

Synonyms Steartrimonium hydrolyzed animal protein Steartrimonium hydrolyzed collagen Stearyltrimonium hydroxyethyl hydrolyzed collagen Trimethyloctadecylammonium hydrolyzed animal protein Definition Quaternary ammonium chloride formed from a terminally epoxide substituted stearyl trimethyl ammonium chloride and hydrolyzed collagen... 

Epoxide substitution + cyanide alk5me anions Grignard reagents organohthimn reagents enolate anions... 

Synthesis of an optically active xy-sutetituted polyester 15 by lipase-catafyzed polymerization has been demonstrated [38]. A highly enantioselective polymerization of a chiral, epoxide-substituted diester 13 with 1,4-butanediol 14 was performed iBing Porcine pancreatic lipase (PPL) as catalyst. The molar... 

Epoxy vinyl ethers of type (183) have been observed to cyclize with high regio-and stereo-specificity on treatment with Lewis acids. The size of the new carbocyclic ring is governed not only by the side-chain length, n, but also, predictably, by the immediate epoxide substitution pattern. 

---