Methyl acrylate, photocycloaddition

Several Ar-alkyl-2-oxo-l,2,3,4-tetrahydroazocine-3-carbonitriles and -carboxylates (88) have been obtained in very low yields by an unusual photocycloaddition of 2-pyridinones and acrylonitrile or methyl acrylate (80T81). The major products are the bicyclo[4.2.0] adducts (89). 

Photocycloadditions of naphthalene derivatives to alkcnes have been recently reviewed.60 Examples of such reactions are the photocycloaddition of naphthalene to 2,3-dihy-drofuran,61 of 4-methoxy-l-naphthonitrile to acrylonitrile62 and of 2-trimethylsiloxynaph-thalene to methyl acrylate.63 2-Naphthols undergo cycloaddition with ethene in the presence of aluminum trihalides only.64 Other bicyclic aromatic compounds, e.g. A-acylindoles65-67 and /V-methylphenanthrene-9,10-dicarboximide,68 have also been studied in detail. Irradiation of 5/f-dibenzo[u,i7]cyclohepten-5-one (21) and dimethyl 2-methylfumarate (22) in dioxane gives the cyclobutane adduct 23 in 73% yield.69... 

The possibility of the intermediacy of the triplet state of benzene itself has been discussed by Atkins et al. [108], Photoaddition of alkenes to arenes is often accompanied by the formation of dimers of the alkene, a reaction sensitized by triplet benzene. With methyl acrylate and methyl vinyl ketone, however, it was found that the ratio of ortho cycloadducts to alkene dimers increased with the concentration of benzene. Because the yield of T, benzene increases with benzene concentration, these results might indicate that ortho photocycloaddition of aery-... 

The scope of this approach was widened by the observation of excellent enantioselectivities in intermolecular [2+ 2]-photocycloaddition reactions with various alkenes [62,71]. In the presence of an excess amount of alkene, 4-me thoxy-2-quinolone (57) was converted with high chemo- and regioselectivity to the exo and endo cyclobutanes 59 and 60. With 4-penten-1-ol (58a), allyl acetate (58b), methyl acrylate (58c), and vinyl acetate (58d), the exo diastereomers 59a-d were formed with high simple diastereoselectivity and in high yields (80-89%), Under optimized irradiation conditions (2.4 eq. of host 44 or ent-44, — 60°C), high enantiomeric excesses were achieved in all instances, as depicted in Scheme 22. These enantiomeric excesses are unprecedented for an intermolecular photochemical reaction. 

The photoaddition of methyl acrylate to pyridones (49) gave the three [2 + 2] cycloaddition products (50), (51), and (52).Similar observations have been reported previously.A patent has been lodged which deals with the photoad-dition of alkenes (RCH=CH2 R = H, CN, or MeC02CH2) to the pyridones (53) to yield the adducts (54) and (55). The photocycloaddition of vinyl acetate to the pyridinones (56) affords the head-to-tail adducts (57) preferentially. ... 

Mizuno, Pac, and co-workers reported photo-Michael reactions via the 2n+2n photocycloaddition-hydrolysis sequences of silyl enol ethers with electron-deficient alkenes such as acrylonitrile, methyl acrylate, and 1-cyanonaphthalene. - Similarly, regioselective 2jr+27l-photocycloaddition of 1-trimethylsiloxynaphthalene with... 

The regiochemical and stereochemical courses of the photocycloaddition of A-acylindoles with monosubstituted olefins such as methyl acrylate and vinyl acetate, as well as the possible mechanistic pathways for these reactions, have been the subject of several reports. In one of the earliest examples, the photocycloaddition of 1 -benzoylindole (8) and methyl acrylate (9) produced the compound 10, which was then converted via a short synthetic sequence to a variety of 2a,7b-dihydrocyclobut[h]indole derivatives 11 (Scheme 2). These compounds were in turn converted to the corresponding l//-l-benzazepines 12, through silver ion-catalyzed thermolysis reactions at 100-160°C [14, 15]. 

The photocycloadditions show all the characteristics of concerted reactions, including stereospecificity and regioselectivity. Concerted 1,3-dipolar additions are known to proceed via a two-plane orientation complex. For the case of diphenylazirine and methyl acrylate, there are two possible orientation complexes (26 or 27). The interaction of substituent groups in the syn complex 26 can be of an attractive (tc overlap, dipole-dipole interaction) or of a repulsive nature (van der Waals strain). Both effects are probably negligible in the anti complex 27. The ratio of the two steric courses syn and anti) functions... 

The regiospecificity of the olefin cycloaddition reaction depends on the substituent groups present on the double bond. Thus, acrylonitrile and methyl acrylate react with various nitrile ylides to give only the 4-substituted regio-isomers (i.e., 16). Photocycloaddition of arylazirines to a-methylacrylo-nitrile and methyl methacrylate, on the other hand, give adducts of type 33 and 34 in a 3 2 ratio. ... 

The photocycloaddition of 2tf-azirines to electron-deficient olefins produces d -pyrrolines as primary photoproducts. Some of the dipolarophiles used include acrylic esters, acrylonitriles, fumaric and maleic esters, methyl allenecarboxylate, norbornene, and l,2-dicyanocyclobutene. Similarly, styrenes and vinylpyridines undergo smooth photocycloaddition to 2H-azirines. Addition of acetylene derivatives to the transient nitrile ylide gives 2H-pyrroles (18, 20) which rearrange to pyrroles (19) if the C-2 atom is monosubstituted. 3-Phenyl-2/f-azirines have been found to cycloadd to vinylphosphonium salts and to vinyl sulfones. The initial adducts (22 and 24) undergo ready loss of the phosphorous or sulfur substituent to give 2H-pyrroles (23 and 25). ... 

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