Styrylcoumarin

It appears reasonable to assume from the dramatic changes in the supramolecular assembly of fluorine-substituted coumarin, 4-styrylcoumarin, and 1,4-diphenyl-butadiene that significant contributions to the lattice energy arise... 

As mentioned earlier, the 4-styrylcoumarin molecule crystallizes in two different modifications [48], Controlled addition of coumarin (2.5-20% by molar ra-... 

Table 5 Crystal Data of the Polymorphic Forms of 4-Styrylcoumarin...

Fig. 6.26 Schematic diagram of the different photoreaction pathways for the triclinic needles and monoclinic prisms of 4-styrylcoumarin 6-XLI. (From Moorthy and Venkatesan 1994, with permission.)...

Moorthy, J. N. and Venkatesan, K. (1994). Photobehavior of crystalline 4-styrylcoumarin dimorphs Structure-reactivity correlations. Bull Chem. Soc. Jpn., 61, 1-6. [236f, 236]... 

Styrylcoumarin has been shown to crystallize out of chloroform and hexane in two different polymorphs [30], The crystal structures of the two forms differed in the nature of the molecular packing, and these differences were sufficient to permit different pathways of photochemistry in the solid state. A summary of the crystallographic data obtained on the two forms is located in Table 10. 

The chiral holmium(III)-complex-catalysed Diels-Alder cycloaddition of siloxyvinylindoles (70) with e-deficient olefins (71) formed exo-substituted hydro-carbazoles (72) in up to 99% yield and 94% ee. Alkylation of these cycloadducts gave tricyclic compounds (73) with four continuous chiral centres (Scheme 20). The thermal 4-i-2-cycloaddition reaction of 7-substituted 4-styrylcoumarins with A-phenylmaleimide and tetracyanoethylene in nitrobenzene yielded 3,4-annulated coumarins. The thermal Diels-Alder cycloaddition of ( )-l,3-dihydro-3-phenacylidene-2//-indol-2-ones (74) with l,2-dihydro-2-oxospiro[3//-indole-3,2 -[2H,9a//-pyrido[2,l-fe][l,3]oxazines]] (75) produced complex dispirooxindoline fused [l,3]oxazines (76) with high regio- and stereo-selectivity (Scheme 21). " ... 

Keywords fluoro-substituted styrylcoumarin, [2+2]photodimerization, cyclobutane... 

Similar experiments on 4-(3-fluorostyryl)coumarin produced a modification different from the original one. The new modification yielded a dimer with sv -HH stereochemistry, in contrast to the anti-HY dimer obtained from the original crystalline form [8a,48], Accurate single-crystal x-ray analysis of the new forms showed no evidence for the presence of coumarin in the crystals, at least not in a detectable amount (Table 6). It is interesting that the addition of napthalene instead of coumarin did not produce the new forms in both the styrylcoumarins mentioned earlier. Presumably, the interaction between the COO- units in coumarin and styrylcoumarin may have a role to play in arresting the growth of the original crystalline forms. However, detailed studies are required to understand the exact mechanism. 

Row, T. N. G. (1999). Hydrogen and fluroine in crystal engineering systematics from crystallographic studies of hydrogen bonded tartrate-amine complexes and fluro-substituted coumarins, styrylcoumarins and butadienes. Coord. Chem. Rev., 183, 81-100. [236]... 

Photodimerisation of (61) affords the cw,a t/,cw-head-to-tail product (62). The position of the fluoro substituent appears to play some part in the outcome of the reaction since irradiation of the isomer (63) affords the cis,syn,cis head-to-head dimer. Further studies of the influence of fluoro substituents on the dimerisation of the styrylcoumarins (64) have also been reported. ... 

Moorthy, J.N., Venkatakrishnan, P., Savitha, G. and Weiss, R.G. (2006) Cis-to-trans and trans-to-cis isomerizations of styrylcoumarins in the solid state. Importance of the location of free volume in crystal lattices. Photochem. Photohio. Sci., 5, 903-913. 

The effects of fluorine substitution on crystal packing and topological photodimerization have also been investigated for styrylcoumarins. " Styrylcoumarin 3 yields the centrosymmetric (a-mode, anti-head-to-tail [HT]) photodimer 5 when irradiated in the solid state however, the inclusion of a fluorine substituent dramatically alters the packing mode and steers molecules 4a and 4b to form stereospecdfic photodimers 6a and 6b (P-mode, sy -head-to-head [HH]) by reaction at the styrenic double bonds. 

Vishnumurthy, K., Guru Row, T. N., and Venkatesan, K., Studies in crystal engineering crystal packing, topological photodimerization and structure-reactivity correlations in fluoro-substituted styrylcoumarins, /. Chem. Soc., Perkin Trans. 2, 615-619,1997. 

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