Crotonic acids aldehyde

Synonyms 2-Butenal 2-Butenaldehyde Crotonal Crotonaldehyde stabilized Crotonic acid aldehyde... 

Examples of the Knoevenagel reaction with aldehydes are given under crotonic acid (111,145), P-n-hexylacrylic acid (111,144), sorbic acid (111,145) and furylacryUc acid (V,10). 

Ethyl-3-methylpyridine (also known as aldehyde-collidine ) has been prepared by heating aldehyde-ammonia aldehyde-ammonia and acetaldehyde or paraldehyde aldol-ammonia and ammonia paraldehyde and ammonia <> 11,12 acetamide,1 or acetamide and phosphorus pentoxide ethylene glycol and ammonium chloride ethylidene chloride or bromide and ammonia ethylidene chloride and acetamide, ethylamine, or n-amylamine crotonic acid and a calcium chloride-ammonia complex 1 and by passage of acetylene or acetaldehyde and ammonia over alumina and other catalysts. 

In the first reports on the use of esters of 4-bromo-2-butenoic acid (191a and b, crotonic acid) and of 4-bromo-3-methyl-2-butenoic acid (191c, senecioic acid), the corresponding Reformatsky reactions with benzaldehyde were performed with the old-fashioned procedure, which required heating the haloester, the aldehyde and granulated zinc in benzene/ether mixtures at reflux temperature. 

Examples given in Expt 5.216 include the preparation of non-2-enoic acid starting from hexanal, but-2-enoic acid (crotonic acid) from acetaldehyde, and also hexa-2,4-dienoic acid (sorbic acid) starting from the conjugated aldehyde crotonaldehyde. 

It has been demonstrated that optically active oxetanes can be formed from oxazolidinone 92, a crotonic acid moiety functionalized with Evans chiral auxiliary (Scheme 18) <1997JOC5048>. In this two-step aldol-cyclization sequence, the use of 92 in a deconjugative aldol reaction, with boron enolates and ethanal, led to formation of the syn-aldol 93. This product was then converted to the corresponding oxetanes, 94a and 94b, via a cyclization with iodine and sodium hydrogencarbonate. This reaction sequence was explored with other aldehydes to yield optically active oxetanes in similar yields. Unlike previous experiments using the methyl ester of crotonic acid, in an analogous reaction sequence rather than the oxazolidinone, there was no competing THF formation. 

The gas phase photooxidation of crotonaldehyde has been studied by Blacet and Volman.21 The product is crotonic acid, which condenses out of the system as soon as it is formed. The quantum yield of oxidation was found to increase steadily over the 3660-2380 A. wavelength range. At constant aldehyde pressure, the quantum yield was independent of oxygen pressure at 3130 and 2804 A. At 2537 A., however, the quantum yield increased rapidly with the oxygen pressure and a chain mechanism is likely. Addition of nitrogen at 2537 A. caused a marked decrease in the quantum yield indicating that excited molecules are involved. 

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. ... 

The aldehyde derived from the next higher hydrocarbon of the ethylene series, viz., the four carbon hydrocarbon, butene, is known as crotonic aldehyde because on oxidation it yields an acid known as crotonic acid. As there are two isomeric butenes due to the position of the double bond there will likewise be possible two isomeric aldehydes or butenals. 

Now the aldehyde which yields crotonic acid on oxidation, i.e., crotonic aldehyde, may be prepared by a synthesis which shows clearly that it must have the constitution of the first of these isomeric aldehydes, A 2-buten-al, CH3—CH = CH—CHO. 

Crotonic Acid from Crotonic Aldehyde.—We have previously shown (p. 169), that crotonic aldehyde is A2-butenal because of its synthesis by the aMol condensation of acetaldehyde. On simple oxidation crotonic aldehyde yields crotonic acid which must therefore have the constitution of A2-butenoic acid,... 

From Acetaldehyde and Malonic Acid.—Another synthesis proves the constitution of crotonic acid as A2-butenoic acid. A di-basic acid known as malonic acid has the constitution of di-carhoxy methane HOOC—CH2—COOH. When this acid is heated with acetaldehyde (paraldehyde) and glacial acetic acid condensation occurs as in the synthesis of crotonic aldehyde and in the Perkin-Fittig synthesis (p. 172). A dibasic acid is obtained which loses carbon dioxide and yields a mono-basic acid which is crotonic acid. 

The unsaturated dibasic acids bear the same relation to the saturated dibasic acids, just considered, as the unsaturated mono-basic acids, acrylic acid, crotonic acid, etc. (p. 172), do to the saturated monobasic acids, acetic acid, etc. They are also the oxidation products of the unsaturated hydrocarbons, alcohols, and aldehydes just as oxalic and succinic acids are of the corresponding saturated compounds. As the simplest dibasic acid containing an ethylene unsaturated group will contain two carboxyl groups and also two doubly linked carbon atoms there must be at least four carbons in the compound. This compound will therefore correspond to succinic acid of the saturated series. Now succinic acid may be derived from either butane by oxidation or from ethane by substitution. Similarly the corresponding unsaturated acid may be derived from butene by oxidation or from ethene by substitution. All of these general relationships may be represented as follows ... 

Thus, the chiral 1,3-dioxane system mediates the enantioselective addition of nucleophiles to an aldehyde [132], since the resulting P-alkoxycarboxylic acids 27 can be cleaved by lithium diisopropylamide to give the chiral alcohols 28 with elimination of crotonic acid. 

In 2015, IFF patented the hydroformylation of cyclopentene (Scheme 6.19) [91]. In turn, the formed aldehyde was reacted with MeMgCl to afford the corresponding secondary alcohol. By esterification with crotonic acid, an ester was obtained having fruity, green, fresh, woody spicy, and sweet notes. 

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