Dichlorocinnamic acid

This procedure has been used by the submitters and others to prepare the following cinnamic acids from substituted benzal-dehydes o-nitrocinnamic acid (70%),2 -nitrocinnamic acid (77%),2 w-cyanocinnamic acid (71%),3 o-chlorocinnamic acid (82%),4 m-chlorocinnamic acid (53%),4 -chlorocinnamic acid (73%),4 2,4-dichlorocinnamic acid (70%),4 3,4-dichlorocinnamic acid (81%),4 w-bromocinnamic acid (31%),4 -methoxycinnamic acid (60%),4 and 3,4-dimethoxycinnamic acid (77%).4... 

Davaasambuu J, Busse G, Techert S (2006) Aspects of the photodimerization mechanism of 2,4-dichlorocinnamic acid studied by kinetic photocrystallography. J Phys Chem A 110 3261-3265... 

Preparation 324.—Dichlorocinnamic Acid 3-Phenyl-2 3-dichloro-peopan acid],... 

In a later example [135], it was shown that photodimerization of 3,4-dichlorocinnamic acid (52) proceeds in high yields in various hydrocarbons to give similar mirror-symmetric products with solvent of crystallization. The reaction does not occur in the fluid phase and dimerization of the suspended monomer... 

Dichloro-substituted, methylenedioxy-substituted, or sulfur-containing planar aromatic molecules often crystallize in 3 structures. These effects were utilized to design [2-1-2] photoreactive molecular complexes [30]. Cocrystallization from EtOH of 6-chloro-3,4-methylenedioxycinnamic acid with 2,4-dichlorocin-namic acid and with 3,4-dichlorocinnamic acid (all three cinnamic acids are 13-type [2-1-2] photoreactive crystals) gave the 2 1 and 1 1 complexes, respectively. Irradiation of these complexes yielded mixtures of three P-truxinic dimers in a statistical ratio (Scheme 9). This result, together with the crystal structures of the component acids, indicates that each sheet that is stabilized by an interstack... 

Recent work of Green and Schmidt (1) shows how the packing can be influenced to obtain either of the two reaction products. As they have reported, derivatives of 2,4-dichlorocinnamic acid always pack in a head-to-head arrangement, giving rise to derivatives of jS-truxinic acid. Thus, polymers with the same stereochemistry as V (Reaction 4) should be produced by using the 2,4-dichlorophenyl residue as the guiding group. 

The photochemical (2 + 2)-dimerization between raw -cinnamates contained within a photocrosslinkable dendrimer has been reported. The cycloaddition is accompanied by trans-cis isomerism. The (3-form of raw -2,4-dichlorocinnamic acid dimerizes on irradiation to give the (3-truxinic acid derivative in a first-order kinetic process. Others have studied the influence of substituents on the aryl ring of cinnamic acid, with a view to control crystal engineering. Ito et alJ have reported the photodimerization in the solid state of cinnamic acids (1) as their... 

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