Crotonic hydration

One of the steps in fat metabolism is the hydration of crotonate to yield 3-hydroxybutvrate. The reaction occurs by addition of —OH to the Si face at CM, followed by protonation at C2, also from the Si face. Draw the product of the reaction, showing the stereochemistry of each step. 

Similar kinetics are obtained with a-methylacraldehyde , but with croton-aldehyde the reaction is essentially first order in Mn(III), tending to zero-order only at relatively high [Mn(Ill)]. The oxidation of acraldehyde is viewed as a rapid reaction preceded by a slow acid-catalysed hydration, viz. 

The tetranuclear structure observed for basic zinc/acetate/[Zn40(02CCH3)6] is also observed for basic zinc pivalate and benzoate. Solution studies showed an equilibrium between hydrated basic structures and the hydrated form of 3,1 bridging structures in the presence of a trace amount of water. Zinc crotonate shows a less common basic carboxylate polymeric structure, [Zn5(OH)2 (02CCHCHCH3)8]n.369... 

Classical precedents for these hydration reactions are far fewer than those of the dimerization process, and reveal more complexity in the reaction. Water has been observed to add photochemically to crotonic acid21a>b and to ergotamine.21b Methanol, ethanol, ammonia, and aniline were also found to add photochemically to crotonic acid.21a More recently, methanol and propanol-2 have been observed to add... 

Protection of a hydroxyl group at C-5 in a nucleoside has been performed161 by using crotonic (2-butenoic) and related esters. A remarkably selective removal of the 5 -0-acyl group was observed on treatment of 3 -0-acetyl-5 -0-(4-methoxycrotonoyl)thymidine with 0.05 M hydrazine hydrate in methanol-pyridine for 2 hours at 20°. 

Reaction of 2-aminopyridines with acrylic acid or methacrylic acid in boiling water for 2-20 hours gave betaine hydrates 262 (R3 = H) in 11-88% yields (Scheme 20) (92KGS80). When 2-aminopyridine reacted with methyl metharylate in acetic acid for 24 hours or 2-aminopyridine and its 5-bromo and 5-chloro derivatives reacted with acrylic acid in boiling toluene for 24 hours or 2-aminopyridine reacted with crotonic acid in boiling toluene for 20 hours, 3-(2-pyridylamino)propionic acid derivatives 263 were the products. When 5-chloro-2-aminopyridine reacted with acrylic... 

The palladium [Pd(Ph3)4]-catalysed 3 + 3-cycloaddition of trimethylenemethane with azomethineimines produced hexahydropyridazine derivatives under mild conditions (40 °C).171 The Lewis acid-catalysed formal oxa-[3 + 3]-cycloaddition of a,f+ unsaturated aldehydes with 6-methyl-4-hydroxy-2-pyrone, 1,3-diketones, and viny-logous silyl esters yielded a variety of pyrones at room temperature.172 Croton-aldehyde has been converted to 6-hydroxy-4-methylcyclohex-l-enecarboxaldehyde by an enantioselective 3 + 3-cycloaddition catalysed by proline. This methodology was used in the synthesis of (—)-isopulegol hydrate, (—)-cubebaol, and (—)-6-hydroxy-4-methylcyclohex-l-ene-1-methanol acetate, an intermediate in the total synthesis of the alkaloid magellanine.173... 

Synonyms. Croton-Chloral Hydrate Trichlorobutylidene Glycol. 

Other functional groups may be present in the molecule containing the double bond. Methallyl alcohol, H2C = C(CHjX HjOH, is hydrated by a mixture of 25% sulfuric acid in the presence of isobutyraldehyde to give the cyclic acetal of isobutylene glycol with the aldehyde. Hydrolysis of the acetal by dilute mineral acid gives isobutylene glycol (94%). Hydration of the double bond by aqueous sulfuric acid has been used to make chloro-i-butyl alcohol from methallyl chloride and /S-hydroxybutyric acid from crotonic acid. ... 

Hydroxybutyric acid can be obtained by hydration of crotonic acid with aqueous sulfuric acid.66... 

Tinder the name croton chloral hydrate. It is a colorless liquid, boiling at 160 (320° F.), obtained by the action of C3 on acetaldehyde. 

As with permanganate oxidations, a-hydroxy ketones can be formed as side products. In some cases, structural features make the osmium complex relatively unstable, and in an aqueous medium it can react with water to give a hydroxy-hydrate, which is then converted to an a-keto alcohol. Sharpless et al. developed a procedure that used tert-butyl hydroperoxide with a catalytic amount of osmium tetroxide,367 in the presence of tetraethylammonium hydroxide (EtqN" " OH ). The procedure gave improved yields of the cis-diol and a little a-hydroxyketone, as shown in the conversion of oct-(4 )-ene to a mixture of 258 and 259 in 73% yield. This method is more reliable for oxidation of tri- and tetrasubstituted alkenes than the Upjohn procedure. The reaction was not suitable for base sensitive alkenes, but later work showed that changing the solvent to acetone allowed the use of tetraethylammonium acetate (Et4NOAc) 68 for the hydroxylation of sensitive alkenes such as ethyl crotonate. 

The unexpectedly low K value of crotonaldehyde can be easily explained on the basis of electronic effects, excepting for the observation that its rate of hydration is considerably greater than those of crotonic acid or of propene. A mechanism involving proton attack upon the ethylenic bond would require the sequence of reactivity... 

Protection of hydroxyl groups as crotonate esters. Crotonate (and related) esters, prepared with the corresponding anhydrides, are deacylated by hydrazine hydrate in CHgOH-Py at 20" in 30-45 minutes (equation I). 4-Methoxycro-... 

Most lubricants are made from natural raw materials paraffins from petroleum residues, lignite carbonization, or bimminous shales the natural fatty acids (Cje to Cl 8 acids and mixtures of same), vegetable and animal fats. Further hydration of the fatty acids results in fatty alcohols. The most effective lubricants in technical terms, as well as the most expensive lubricants, are refined mmitanic waxes (C28-C32). Semisynthetic lubricants are based on the conversion of alcohols to esters, metal oxides or hydroxides to salts or amines to amides. FuUy S3mthetic waxes include low molecular PE and PP waxes or copolymers made from ethylene, VAC, acrylic, or crotonic acid. 

Uses Intermediate in mfg. of n-butanol, crotonic acid, sorbic acids mfg. of resin and rubber antioxidants solvent in min. oil purification warning agent in fuel gas for locating breaks and leaks in pipes alcohol denaturant mfg. of butyraldehyde, quinaldine minor amts, in mfg. of maleic acid, crotyl alcohol, butyl chloral hydrate, rubber accelerators in org. synthesis insecticides chemical warfare... 

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