Epoxides acid cleavage

Physical and Chemical Properties. The (F)- and (Z)-isomers of cinnamaldehyde are both known. (F)-Cinnamaldehyde [14371-10-9] is generally produced commercially and its properties are given in Table 2. Cinnamaldehyde undergoes reactions that are typical of an a,P-unsaturated aromatic aldehyde. Slow oxidation to cinnamic acid is observed upon exposure to air. This process can be accelerated in the presence of transition-metal catalysts such as cobalt acetate (28). Under more vigorous conditions with either nitric or chromic acid, cleavage at the double bond occurs to afford benzoic acid. Epoxidation of cinnamaldehyde via a conjugate addition mechanism is observed upon treatment with a salt of /-butyl hydroperoxide (29). 

Epoxides are more reactive than other ethers. This is due to ring strain inherent in any three-atom ring system. The most useful reactions are acidic cleavage and nucleophilic cleavage. 

I n contrast to the relative simplicity of the chromyl chloride oxidation of 2,2-disubstituted-l-alkenes to aldehydes, the rlimmyl acetate and chromic acid oxidations generally lead to epoxides, acids, and carbon-carbon double bond cleavage. For example, chromyl acetate oxidizes 4,4-dimethyl-2-neopentyl-I pentene primarily to l,2-epoxy-4,4-dimethyl-2-neopentyl-pentane in low yield,9 and chromic acid oxidizes the alkene principally to 4,4-dimethyl-2-neopentylpentanoic acid.6,10... 

Bromination of 3,10-epoxycyclo[10.2.2.02,11.04 9]hexadeca-4,6,8,13-tetraene (11) gave (12) and several by-products. Acid cleavage of corresponding epoxide proceeded in a similar fashion.27... 

Androstenolone, 1, can be transformed microbiologically to the 7a,15a-dihy-droxy derivative 2 by the action of Colletotrichium Uni. During formation of the acetal (3), inversion takes place on C-7. Acidic cleavage of 3 results in the triol, 4, which can also be produced by direct acidic catalysis from 2 [12,13]. After selective protection to the 3/l,15a-dipivalate (5), the 15/1,16/1-methylene compound, 6, can be synthetized, and then stereoselectively transformed to the 5/ ,6/ -epoxide, 7. This reacts with triphenylphosphine and tetrachloromethane in pyridine to produce the 7a-chloro derivative, 8. On treatment with zinc and acetic acid, 8 can be converted to the key compound 9, which has a 5/i-hydroxy-6-ene structure. Compound 9 can then be methylenated stereoselectively in the 6/1,7/1 position by the Simmons-Smith method. The last three steps - 10 —> 11 —> 12 — drospirenone -include the build-up of the spironolactone ring, after which water is lost from the molecule and oxidation affords drospirenone. 

The peracid is prepared in 65-75 % yield by the reaction between o-sulfobenzoic anhydride and 30% hydrogen peroxide in acetone solution at —4 to 0°C. The solution is used directly for epoxidation of olefins. Since the reagent contains a strongly acidic group, the initially formed epoxide undergoes acid cleavage to a truns-diol unless a solid buffer such as sodium carbonate is present. The peracid can also be used for Baeyer-Villigcr oxidation and for oxidation of heterocyclic t-amines to N-oxides. ... 

Several conclusions are drawn from the product studies of the reactions of propylene oxide and isobutylene oxide in H O.23 In the acid-catalyzed hydrolysis of propylene oxide, cleavage of the secondary C-O bond is favored by a factor of 2-3 over cleavage of the primary C-O bond. In the acid-catalyzed hydrolysis of isobutylene oxide, cleavage of the tertiary C-O bond is highly favored (>99%). These results show that in acid-catalyzed epoxide hydrolysis, cleavage of the C-O bond leading to... 

Ckavage with ethereal period acid." In the case of water-insoluble compounds, or where a cleavage product is sensitive to aqueous acid, cleavage of a ptc-glycol or an epoxide of the type formulated can be carried out with a solution of periodic acid in ether or tetrahydrofurane. A solution containing about 16 mg./ml. can be prepared by stirring an excess of the powdered peracid with dry ether or THF for... 

BE3 -OEt2 easy-to-handle and convenient source of BF3 Lewis acid catalyst promotes epoxide cleavage and rearrangement, control of stereoselectivity BF3 MeOH esterification of aliphatic and aromatic acids cleavage of trityl ethers)... 

In a continuation of his studies on asymmetric P-lactam synthesis, Evans [42] utilized a,P-epoxyaldehydes 49a and 49b, prepared in two steps from achiral allylic alcohols via Sharpless asymmetric epoxidation and Swern oxidation, as chiral glyoxal synthons for the ketene-imine cycloaddition. Diastereosel-ection was excellent, ranging from 90 10 to 97 3 with overall yield of 50 up to 84% (for Schiff base formation and cycloaddition) after recrystallization or chromatographic purification of the major diastereomer. The sense of asymmetric induction correlated with that obtained in the analogous glyceraldehyde reaction, as established by periodic acid cleavage to aldehydes 51. 

Epoxide-ring cleavage of epoxygermacrone (292) with formic acid to form the ketones (293) and (294) is proposed as a suitable chemical model for... 

There are three principal ionic ring-opening polymerization reactions of epoxides acid-initiated, base-initiated, and coordinate-initiated polymerizations. The acid-initiated reaction involves addition of an active hydrogen compound, HY, such as ethanol, to an epoxide ring and is catalyzed by an acid, HX, such as perchloric acid. The reaction sequence involves formation of an oxonium complex, followed by ring opening by an 8 2 cleavage of an oxonium carbon bond. 

Regioselectivity of C—C double bond formation can also be achieved in the reductiv or oxidative elimination of two functional groups from adjacent carbon atoms. Well estab llshed methods in synthesis include the reductive cleavage of cyclic thionocarbonates derivec from glycols (E.J. Corey, 1968 C W. Hartmann, 1972), the reduction of epoxides with Zn/Nal or of dihalides with metals, organometallic compounds, or Nal/acetone (seep.lS6f), and the oxidative decarboxylation of 1,2-dicarboxylic acids (C.A. Grob, 1958 S. Masamune, 1966 R.A. Sheldon, 1972) or their r-butyl peresters (E.N. Cain, 1969). 

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