Maleic anhydride photoreaction

The prototype of the present surface photografting is the surface photoreaction of maleic anhydride(MAH) onto poly(butadiene) film(15). Although fair improvement of surface wettability was achieved, photoaddition of MAH cannot be applied to other polymers having no ethylenic double bonds. The present process is applicable to almost all polymers except for poly(tetrafluoroethy-lene) and its analogues. 

Acetone-sensitized [2+2]-photocycloaddition of 2(3//)-oxazolones 247a to maleic anhydride and dimethylmaleic anhydride gives the corresponding anti-cyclobutane cycloadducts 253 as the major products. Similar photoreaction of 2(37/)-oxazolones with 1,6-anhydro-4-(9-benzyl-2,3-dideoxy- 3-D-e 7t/ira-2-hex-enopyranose 254 results in the exclusive formation of the anh-cyclobutane-type adduct 255 (Fig. 5.61). ... 

If the alkene, from which the ortho photocycloadduct is derived, is a powerful dienophile, a thermal Diels-Alder reaction between adduct and alkene may take place during the irradiation so that a 2 1 alkeneiarene adduct is formed. Such adducts are quite stable and can easily be purified. Their structure contains all the regiochemical and stereochemical information of the primary 1 1 ortho adduct. This Diels-Alder reaction occurs spontaneously with the alkenes maleic anhydride, maleimide, and their derivatives, as discussed in the sections of this chapter that deal with photoreactions of ground-state charge-transfer complexes (maleic anhydrides) and reactions of excited alkenes with ground-state arenes (maleimides). Ortho adducts formed from other alkenes have often been identified via their reaction with a good dienophile. 

Ia2a. Sensitized photopolymerization of N,N -alkylenebisdichloromaleimides. The photodimerization of maleic anhydride, raaleimide and derivatives has been studied by several research groups (170-172). The benzophenone-sensitlzed photoreaction of N,N -alkylenebisdichloromaleimides [95] with a long polymethylene chain between the two chromophores resulted in the formation of macromolecules (173). The data are collected in Table 12. 

Unsaturated compounds also yield cyclobutane derivatives in cycloaddition photoreactions sensitized by benzophenone,61,62 examples being cycloaddition of maleic anhydride and various alkyl and halo maleic anhydrides and male-imides.63 65... 

Under the influence of light, maleic anhydride can undergo reactions with a variety of substrates. Common types of reactions involve [2 4- 2] cycloadditions and/or processes where radical intermediates occur. When radical intermediates do occur, often useful nonpolymeric adducts are obtained. So, in addition to the photoreactions, radical reactions of MA yielding nonpolymeric products are also discussed in this chapter. 

The first investigation of the photoreaction of maleic anhydride with an olefin can be credited to Griffin and coworkers.It was observed that a thin layer of MA deposited on glass, upon exposure to an UV lamp, produced a dimer 21. 

Maleic anhydride and hexamethylbenzene form a 1 1 charge-transfer complex in methylcyclohexane solvent with a UV maximum at 340 tx. Ultraviolet irradiation of these solutions brings about the formation of carbon dioxide, pentamethylbenzylsuccinic anhydride, and resinous products (see Chapter 6). Analytical data suggest the polymeric material has a decarboxylated MA building block. Charge-transfer complexes were not detected in solid-state mixtures of MA and pentamethyl-benzene. Ultraviolet irradiation of these solid mixtures gives cyclic dimer, 1,2,3,4-cyclobutanetetracarboxylic anhydride 2, and resinous products. Pentamethylbenzylsuccinic anhydride, due to the possible absence of charge-transfer complexes, was not isolated from the solid-state photoreaction. 

In an attempt to trap fulvene 2 by the Diels-Alder reaction with maleic anhydride, another new photoreaction was discovered/ A cycloadduct was obtained which was suggested to be formed by direct addition to the excited state of benzene. Since then, photoadditions of alkenes to benzene and substituted benzenes have been studied extensively and become a powerful tool for synthetic approaches to complex polycycHc compounds. - ... 

Photosensitized reaction of 15c with maleimide 19g at low temperature (-10 to -20°C) affords the exo-[4-1-2]-adduct 16 as a major product, together with the [2-1-2]-adduct 17 (Scheme 11). The same reaction was carried out at room temperature to afford the bis-adduct 27, which was formed via decarboxylation of 16cg followed by addition of another molecule of 19g, in addition to the formation of 17cg. The low-temperature photoreactions of 2-pyrones 15a, 15b with 19g or 19g also gives [4-1-2]-adducts 16ag, 16bg, and [2-1-2]-adduct 17bg. Similar photoreactions of 2-pyrones 15b, 15c with maleic anhydride afford exo-[4-1-2]-adducts (major products) and/or [2-1-2]-adducts. Photosensitized reaction of 15a with dimethyl acetylenedicarboxylate affords 1, 2, 4-tris(methoxycarbonyl)benzene 28 in 50% yield byway of decarboxylation of the [4-1-2]-adduct, which was difficult to isolate even from the reaction mixture obtained from the low-temperature irradiation (Scheme 12)." Similar reactions of 15a with... 

R, the photoreactive group, is attached through the appending group X which can be — NH such as in an amide or an oxygen of an ester group. By this means a wide variety of photoreactive groups have been appended to styrene-maleic anhydride copolymers. Merrill and Unruh [28] prepared aromatic azide polymers which are soluble in aqueous bases by reaction of azidophthalic anhydride with poly(vinyl alcohol). 

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