Olefinic amines reactions with arenes

The initial step in the addition reactions of arenes and aryl olefins with tertiary amines is electron transfer quenching of the singlet arene or aryl olefin acceptor by a ground state amine donor. The free energy of electron transfer can be calculated using Weller s equation (Eq. I) ... 

Yasuda and Pac and their co-workers " have significantly extended the scope of ET-sensitized addition in their studies of the photoamination reactions of arenes and aryl olefins (Scheme 2). DCNB is a powerful electron acceptor (Table 1) capable of oxidizing the singlet slates of most arenes and aryl olefins (Table 2). Benzene does not undergo photoamination however a di-methoxy derivative and biphenyl are reactive. Photoamination products are generally obtained in high preparative yield using ammonia or primary amines however, secondary amines can only be used successfully with arenes such as anthracene which have oxidation potentials lower than those of secondary amines. When the amine oxidation potential is comparable to... 

Intramolecular addition reactions of arenes and aryl olefins with secondary and primary amines have proven to be of broader scope than the analogous reactions with tertiary amines. The intramolecular addition of nonconjugated o-allylanilines 51 to yield the 2-methylindolines 52 was reported by Koch-Pomeranz et al. in 1977. Intramolecular electron transfer from the singlet aniline to the ground state alkene followed by N-H proton transfer to the alkene terminal carbon was proposed to account for the regioselective formation of indolines. Proton transfer to the internal carbon would yield tetrahydroquinolines, which were... 

The synthetic and mechanistic aspects of photoaddition reactions of amines with excited states of arenes and aryl olefins have been extensively investigated [10-12, 277],... 

Whereas addition reactions of singlet aryl olefins and arenes with secondary and tertiary amines are common, addition of ammonia has not been reported and addition of primary amines... 

The photochemical reactions of aryl olefins and arenes with secondary and primary amines are assumed to occur via a sequential eleetron transfer-proton transfer meehanism similar to that for tertiary amines (Scheme I). Exciplex fluorescence is not observed in solution however, weak exciplex fluorescence has been reported for the slyrene-diethylamine system in a su-personie jet. Rate constants for quenching of strong acceptors such as stilbene and styrene by EtjNH are diffusion controlled. 

Whereas most reactions of singlet arenes and aryl olefins with secondary amines result in N-H addition, there are exceptions to this generalization. Cookson et al. reported that irradiation of 1-phenylcyclohexene in isopropylamine yielded a mixture of N-H and a-C-H adducts. Gilbert and co-workers ° found that the reaction of benzene with dimethylamine yields N-H adducts, whereas pyridine reacts with diethylamine to yield the substitution product 11, which presumably is formed by aromatization of the a-C-H adduct. Irradiation of stilbene and indole in mixed crystals yields both N-H and C-H adducts, product ratios being dependent upon the reactant ratio. Investigation of the reactions of 9-cyanophenanthrene with primary and secondary... 

PHOTOADDITION REACTIONS OF AMINES WITH ARYL OLEFINS AND ARENES Frederick D. Lewis... 

With Palladium In 1979, Diamond et al. [39] reported the first Pd-catalyzed chelation-assisted olefin arylation using aromatic amines as substrates. The Pd-cat2ilyzed oxidative direct vinylation of arenes is well known, and the Fujiwara [40] reaction, for example, is a method for the Pd-catalyzed oxidative arylation of olefins. 

A simple CUCI2/O2 catalyst system for the oxidative cyclization of N-methylanilines with electron-deficient olefins to substituted tetrahydroquionoline was developed by Hirano, Miura, and coworkers (Scheme 8.90). One C(sp )-H bond of methyl group and one C(sp )-H bond of arene were cleaved in this reaction. The present efficient copper/oxygen catalytic system provides a direct access to tetrahydroquionoline frameworks easily [160]. Seidel et al. reported CuBr-catalyzed oxidative Povarov reactions of various Af-aryl amines to synthesize tetrahydroazepine derivatives in moderate yields using TBHP as the terminal oxidant. Both the C(sp )-H and C(sp )-H bonds are active during the process [161] (Scheme 8.90). 

Upon oxidation, the subsequent radical cation can decompose in a number of different ways to generate reactive intermediates (Scheme 10.1). The first possibility involves direct H-atom abstraction of the a-C-H bond of the oxidized amine (I) to generate an iminium ion (II), which is susceptible to nucleophilic attack via polar reaction mechanisms (pathway a). Deprotonation of I may also form a carbon-centered radical species (III) that can react with typical radical traps, such as olefins or arenes (pathway b). Generation of the iminium ion may also occur indirectly through oxidation of III via SET to the photocatalyst or another oxidant (pathway c). Finally, radical cation I can undergo non-productive pathways such as back-electron transfer with the reduced photocatalyst (PC" ) to re-generate the neutral amine and PC" (pathway d). 

Lewis, F.D., Photoaddition reactions of amines with aryl olefins and arenes, in Advances in Electron Transfer Chemistry, Vol. 5, Mariano, P.S., Ed., JAl Press Inc., Greenwich, CT, 1996, p. 1. 

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