Cinnamic acid, hydroxy derivatives trans

There are several examples in the literature where similar cis-trans isomerizations of o-hydroxy cinnamic acid derivatives have been used to deliver fragrances. For example, ester 76, which was absorbed into cloth and exposed to sunlight, released its fragrant alcohol moiety, whereas samples that were stored in the dark did not... 

Coumaric Acid, Coumarinic Acid or Hydroxy-cinnamic Acid [called Cumarsaure, Cumarinsaure, (Oxyphenyl)-acrylsaure or Oxy-zimtsaure in Ger], CgH803 mw 164-15, O 29-24%. This compd exists as ortho-, meta - para - derivs. The ortho deriv is known in both trans cis forms ... 

Pr, Bu, Ph etc) to benzonitrile oxide are oxidized to trans-4-hydroxy-2-isoxazolines 10 by t-butyl hydroperoxide (94TL7493). A reversal of regiochemistry was observed in the reaction of aromatic nitrile oxides with derivatives of cinnamic acid the methyl ester gave a mixture of the esters 11 and 12 (R = OMe), in which the former predominated, while in the case of M,N-diethylcinnamide the amide 12 (R = NEt2) was the main product (94TL6473). 

Basic catalysts other than alkali acetates have been employed in the Perkin reaction thus salicylaldehyde condenses with acetic anhydride in the presence of triethylamine to yield coumarin (the lactone of the cis form of o-hydroxy-cinnamic acid) together with some of the acetyl derivative of the trans form (o-acetoxycoiimaric acid) ... 

As p-hydroxy-cinnamic acid can exist in either the or trans configuration, both were tested. The data (Table III) showed that the -isomer was more active than the trans-isomer. Saturation of the double bond in the aliphatic portion of the molecule was investigated by testing the dihydro-derivatives of p-hydroxycinnamic and 3,4-dihydroxycinnamic acids. The dihydro-acids were slightly more active than the corresponding cinnamic compounds. 

A one-pot two-step synthesis of hydroxystilbenes with trans selectivity was developed through a modified Perkin reaction between benzaldehydes and phenylacetic acids bearing 4- or 2-hydroxy substitution at the aromatic ring [67]. The reaction was performed under mild conditions in the presence of piperidine-methylimidazole and polyethylene glycol under microwave irradiation. As a result, 71% yield of ( )-4-chloro-4 -hydroxy-3 -methoxystilbene from 4-hydroxy-3-methoxybenzaldehyde and 4-chlorophenylacetic acid was obtained. A microwave-induced one-pot process for the preparation of arylethenes has been patented [118]. For the preparation of a series of arylethenes (I R -R = H, OH, OMe, AcO, halo, NO2 R, R, R = OH, AcO R= H, substituted aryl), reaction of 2- or 4-hydroxy substituted cinnamic adds or derivatives in the presence of a base, under reflux or microwave irradiation, has been used. For example, a mixture of a-phenyl-4-hydroxy-3-methoxycinnamic acid, NaHC03, methylimidazole, and polyethylene glycol was microwaved at 200 W and 180 °C for 10 min to give 96% 4-hydroxy-3-methoxystilbene. 

The coumarins in question are derivatives of o-coumaric acid. Cinnamic acids which may carry hydroxy and methoxy groups, are hydroxylated in the o-posi-tion to give the coumarins shown in Table 49. An important step in this biosynthetic pathway is a light-dependent, nonenzymatic cis-trans-isomerization of the cinnamic acid side chain. Glucosylated derivatives are important intermediates. Glucosides of coumarinic acid derivatives predominate in fresh plants. Cleavage of glucose and formation of coumarins usually is the result of the break down of... 

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