Intramolecular addition reactions styrene

Lewis, F. D., Bassani, D.M., Reddy, G.D., Styrene Amine and Stilbene Amine Intramolecular Addition Reactions, Pure Appl. Chem. 1992, 64, 1271 1277. 

These intramolecular addition reactions are remarkable in that they have no intermolecular counterpart. In fact, A/,W-dialky-lamides and tetraalkyl ureas fail to quench styrene fluorescence. However, photoaddition of some 1,1-diarylethylenes and tetra-methylurea has been reported. The intramolecular reactions are proposed to occur via weakly bound nonfluorescent singlet exciplex intermediates, which undergo a-C-H transfer to yield the biradical precursors of the observed products. A triplet mechanism was excluded based on the failure of sensitization by xanthone or quenching by 1,3-pentadiene. The involvement of charge transfer is consistent with the requirement of polar solvents for these reactions. The quantum yields for adduct formation from 19 and 25 are much higher than those of their p-methoxy derivatives, in which the styrene is a much weaker electron acceptor. ... 

Products of addition to styrene double bonds can arise as a result of light induced electron transfer reactions. Lewis has studied the intramolecular reaction of l-phenyl-w-amino alkenes (422) 289,290 products arise from electron transfer from the amine nitrogen to the excited state of the styryl group followed by intramolecular proton transfer in the radical ion pair produced. The resultant biradical then couples to yield the isolated products (423) and (424). Sensitisation of the intermolecular analogue of this reaction by 1,4-dicyanobenzene has been reported and is proposed to occur by electron transfer from the styrene to the excited state of the sensitiser followed by attack of an amine on the styrene radical cation. This ultimately leads to the product of anti-Markovnikov addition of the amine across the double bond of the styrene. This is similar to the sequence long since established by... 

Irradiation of phenanthrene in the presence of the electron deficient styrene (376) and hexamethyldlsilane is reported to yield (377) by a mechanism involving electron transfer to the styrene. The reglochemlstry of the light Induced intramolecular addition of eunines to excited styrenes in (378) has been examined.This reaction also proceeds by electron transfer from the amine to the excited styrene chromophore. 

Aoyama and co-workers have also investigated the intramolecular photoamination reactions of several tertiary (aminoal-kyl)styrenes. Irradiation of the (dibcnzylaminoalkyl)styrenes 28 and 29 results, respectively, in the formation of the pyrrolidine 30 and the piperidine 31 as mixtures of diastereomeric adducts. Irradiation of the (aminoalkyl)styrene 32 provides the bicyclic adduct 33 in good yield. Unlike the highly regioselective intramolecular addition of 22 and intermolecular addition reaction of stiibene with W,AI-dimethylisopropylamine (Scheme 3), the intramolecular reaction of the A/-methyl-Af-isopropylamine 34 yields a mixture of adducts 35 and 36 which result from N-methyl and Al-isopropyl hydrogen abstraction, respectively. 

The failure of tertiary (AI,IV-dimethylaminoalkyl)arenes and stilbenes to undergo intramolecular addition may reflect structural differences between inter- vs. intramolecular exciplexes. Polar solvents are generally required for the observation of in-termolecular addition reactions of tertiary amine exciplexes. Equilibration between solvent-separated and radical ion pairs may be necessary in order to achieve an appropriate reaction trajectory for a-C-H proton transfer. In the case of intramolecular exciplexes with short chain linkers, electron transfer in polar solvents may occur in extended geometries which are inappropriate for proton transfer and chain folding may not compete effectively with exciplex decay. The exceptions to these generalizations, benzene and styrene, form more localized anion radicals which undergo both inter- and intramolecular reactions with tertiary amine cation radicals in nonpolar solvents. 

The synthesis and reactions of cationic platinum(II) complexes containing alkenes has been reviewed. New cationic complexes of the type [Pt(T 2-alkene)(X)(tnien)l [C104] (alkene = ethene, propene, styrene, (E)- and (Z)-but-2-ene X = Cl, NO2 tmen = N,N,N, N -tetramethylethylenediamine) have been reported 2 and the intramolecular addition of the oxygen of the nitro ligand onto the cw-alkene described 3 in the case of X = NO2 and alkene = propene or ( )-but-2-ene. 

Haward et al.t have reported some research in which a copolymer of styrene and hydroxyethylmethacrylate was cross-linked by hexamethylene diisocyanate. Draw the structural formula for a portion of this cross-linked polymer and indicate what part of the molecule is the result of a condensation reaction and what part results from addition polymerization. These authors indicate that the crosslinking reaction is carried out in sufficiently dilute solutions of copolymer that the crosslinking is primarily intramolecular rather than intermolecular. Explain the distinction between these two terms and why concentration affects the relative amounts of each. 

Intramolecular oxonium ylide formation is assumed to initialize the copper-catalyzed transformation of a, (3-epoxy diazomethyl ketones 341 to olefins 342 in the presence of an alcohol 333 . The reaction may be described as an intramolecular oxygen transfer from the epoxide ring to the carbenoid carbon atom, yielding a p,y-unsaturated a-ketoaldehyde which is then acetalized. A detailed reaction mechanism has been proposed. In some cases, the oxonium-ylide pathway gives rise to additional products when the reaction is catalyzed by copper powder. If, on the other hand, diazoketones of type 341 are heated in the presence of olefins (e.g. styrene, cyclohexene, cyclopen-tene, but not isopropenyl acetate or 2,3-dimethyl-2-butene) and palladium(II) acetate, intermolecular cyclopropanation rather than oxonium ylide derived chemistry takes place 334 ). 

Iron salts (e.g. FeCls) have been identified as new catalysts for intramolecular hydroamination. A number of olefinic tosylamides underwent the reaction at 80 °C to form the corresponding the N-tosylpyrrolidine derivatives in good yield.63 The same salt can also catalyse Markovnikov addition of electron-rich arenes and heteroarenes to styrenes, giving rise to 1,1-diarylalkanes at 80 °C.64... 

In contrast, a Markovnikov addition of water was reported in the irradiation of a variety of o-hydroxystyrenes, again in aqueous acetonitrile, with the formation of 2-(2-hydroxyphenyl)ethanols. In this case, an intramolecular proton transfer from the excited state of the styrene was envisaged as the first step of the reaction [51]. A similar mechanism was postulated in the photohydratation of m-hydroxy-1,1 -diaryl alkenes that gave the corresponding 1,1-diarylethanols, although direct protonation of the P-carbon by water competed in some cases [52]. 

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