2,3-Butanediol substitution reactions

Halogens add to butenediol, giving 2,3-dihalo-l,4-butanediol (90,91). In a reaction typical of aHyhc alcohols, hydrogen haUdes cause substitution of halogen for hydroxyl (103). 

RuCl3-3H20 combined with P(C6H5), catalyzes a reaction of N-substituted anilines with 2,3-butanediol or 1,2-cyclohexanediol to give 2,3-dimethylindoles or 1,2,3,4-tetrahydrocarbazoles. 

Epoxidation of a,P-unsaturated acids (1.475). This reaction, first reported in 1959, has seen limited use because of moderate yields. Actually, yields are considerably improved by increasing the amount of catalyst and by increasing the pH to 5.8-6.8. The rate of epoxidation is markedly affected by substitution on the double bond, being enhanced by either an oc-alkyl or a p-c/y-alkyl substituent The rate is also increased by addition of butanediol, lactic acid, or tartaric acid. 

Dienes react with ozone at one or both double bonds to give carbonyt compounds. When 1,3-cyclohexadiene is dissolved in dichloromethane at -78 °C and treated with 1.5 mol of ozone in dichloromethane solution and the resulting ozonide is stirred overnight at 0 °C with dimethyl sulfide, 2-hexenedial is obtained in 67% yield. If, on the other hand, an excess of ozone is passed through a solution of 1,3-cyclohexadiene at -78 °C until a blue color appears, both double bonds are ozonolyzed, and a 70% yield of 1,4-butanediol is obtained by reducing the reaction mixture with lithium aluminum hydride (equation 138) [92]. More substituted double bonds react with ozone preferentially. 

With Miscellaneous Compounds. Several mechanistic studies have been performed recently on reactions of "auxiliary stabilizers with 4-chloro-2-hexene, both in the presence and in the absence of metal salts (82,87,88, 89,90). The stabilizers used were phosphites (82,87), phosphines (82,87), epoxides (88), 2-phenylindole (89), and the bis(j8-aminocrotonate) ester of 1,4-butanediol (90). Important mechanistic features delineated in this work included substitutive removal of allylic... 

Fragmentation processes of photoinitiators form a number of volatile products, which may contribute to indoor air pollution. Benzaldehyde and alkyl-substituted benzalde-hydes are usual components, because Norrish-I is the most important reaction for cleavage. Awell known example is l-phenyl-2-hydroxy-2-methyl-propane-l-one (PHMP). a-Cleavage generates two radicals in the first step. The benzoyl radical may recombine to form benzil, reduction of PHMP leads to l-phenyl-2-methy 1-1,2-propane and acetone, and recombination of the 2-hydroxypropyl radical gives 2,3-dimethyl-2,3-butanediol... 

The method could be applied to reduce 1,3-diaryl-1,3-diketones to 1,3-diaryl-1,3-propanediols in 93-100% yields and high ee s (>97% ee). The products were obtained as a mixture of diastereomers (81 19 - 90 10) and could be purified by recrystallization.Symmetrical 2-substituted-l,3-diaryl-1,3-diketones underwent reductive desymmetrization to give rise to /8-hydroxyketones (45-97% yields) in high ee s (>91% ee) and diastereoselectivities (dr>99 l) (eq 32). Unsymmetrical 2-alky 1-3-ary 1-1,3-diketones were reduced chemoselectively at the aryl-substituted carbonyl group to yield 2-alkyl-3-aryl-3-hydroxyketones (41-48% yields) in high ee s (>95%) and diastereoselectivities (( >97 3). The yields could be further improved by the addition of a stoichiometric amount of sodium methoxide in a one-pot reaction. 1,4-Diaryl-1,4-butanediones were reduced to enantiopure l,4-diaryl-l,4-butanediols (60-100% yields), which... 

Kinetic studies have been made on the thermal decomposition of a poly(oxypropylene)triol-toluene di-isocyanate copolymer foam. Following a diffusion rate-controlled step, the cellular structure collapses to a viscous liquid and degradation then occurs on a random scission basis. Products of degradation of A-monosubstituted and A A-disubstituted polyurethanes have been analysed by direct pyrolysis in the ion source of a mass spectrometer. The mono-substituted polymers depolymerize quantitatively to di-isocyanates and diols, whereas the disubstituted materials decompose selectively to secondary amines, olefins, and carbon dioxide. The behaviour of the monosubstituted polymers has been confirmed in an i.r. study of the degradation of model compounds. A study of the thermal degradation in vacuum of polyurethanes prepared from butanediol, methylene bis(4-phenylisocyanate), and hexanedioic acid-ethylene glycol-propylene glycol polyesters has been reported and reaction mechanisms proposed. ... 

Polycarbamates are polymers with carbamate (formerly urethane) or N-substituted carbamate linkages in the backbone (-NR-C0-0-). Polycarbamates or polyurethanes are prepared by the reaction of dihydric alcohols and diisocyanates, e.g. by reaction of 1,4-butanediol and hexamethylene diisocyanate (see Fig. 2.2.6). The properties depend on the number of CH2-groups. 

An optically pure chiral alkene-Fp complex is formed by reaction of the (Z)-2-butene-Fp complex with (/ ,R)-2,3-butanediol. Nucleophiles are added to this complex in a complete stereoselective way. Ring opening of the cyclic alkyl-Fp complexes with trimethylsilyl triflate leads to substituted vinyl ether-Fp complexes as pure enantiomers. The configurational stability of those complexes is limited, however, which requires immediate demetalation to the organic products (Scheme 4-75). ... 

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