Binaphthyls cation-radicals

In terms of nitration, the system (NaN02 + CF3SO3H) is of no interest. At the same time, dimerization in this system can be attractive. For the last direction, CF3SO3H (or FSO3H) is necessary to produce binaphthyl derivatives more preferentially than nitro compounds (Tanaka et al. 1996). This work was preceded by the observation that the reaction of NO+AICI4 with 1-methyl-, 1,2-dimethyl-, 1,3-dimethyl, or 1,8-dimethylnaphthalenes in liquid SO2 leads to a partial a,a-dimerization (see Borodkin et al. 1993). Ozeryanskii et al. (1998) published the dimerization of l,8-Af,Af-bis(d imethylamino)naphthalene by the action of NOj in CHCI3. This reaction is accompanied by the formation of 4-nitro-l,8-A,A-bis(dimethylamino)naphthalene. Both gronps of anthors consider cation-radicals of the initial substrates as intermediate species. 

Polymers 340-343 have a deep red or brown color probably related to the presence of conjugated polynuclear units. A similar color was noted in the polymers derived from cation-radical polymerization of 1,1 -binaphthyl and o-terphenyl. In these cases the color was attributed to the presence of cation-radicals of perylene and triphenylene structural units [193,201,203]. Perylene units are possible in polymers 340-343 (Fig. 46). 

The vinylcyclopropane radical cation, generated at 77 K by X-irradiation of (139) in a Freon-113 matrix, was shown to rearrange at 105-110 K to afford two ring-opened distonic radical cationic species.300 The rearrangement reactions of the radical cations of 1,3- and 1,4-pentadiene and cyclopentene and the formation of spin adducts with 2.4.6-tri-/-butylnitrosobenzene (BNB) are discussed. The pulse radiolysis of 1,1 -binaphthyl-2,2,-diyl hydrogenphosphate (BiNPCUH) (140) in deaerated f-butanol at... 

The nitration of 1 with one equivalent of HNO3 in H2SO4 gave two products the 4-nitro derivative 108 and the binaphthyl proton sponge 36 in 70 and 10% yield, respectively164,187. The reaction proceeds even at —20 °C and is completed within 5 min. These conditions are essentially milder than those for the naphthalene nitration. This is somewhat astonishing, since in such an acidic medium the diamine 1 seems to exist entirely as cation 1 H+, which should be more inert towards electrophiles than the naphthalene itself. One of the reasonable explanations of this discrepancy is that the reaction proceeds via very small equilibrium amounts of the non-protonated 1 or the non-chelated cation l H+-c. Any of them, under the action of the nitronium cation, is oxidized to the radical cation 1+ , which either dimerises or reacts with N02 to give the reaction products 36 and 108 (Scheme 27). There are several indirect pieces of evidence in favour of this. One of them... 

The DCA-sensitised reactions of the phosphate (352) in acetonitrile using X. > 355 nm results in formation of the corresponding radical-cation which undergoes bond fission with the formation of the binaphthyl (353) and the phosphate (354), An analogous reaction takes place with (355) to give (353) and the phosphate (356). The yields of product are low as are the quantum yields and interestingly the phosphates (357) are unreactive under these conditions. 

Binaphthyls. Naphthalene derivatives undergo oxidative dimerization on treatment with NaNOj and triflic acid in MeCN. Radical cation intermediates are involved. 

DCA sensitisation of tri-1-naphthyl phosphate or di-l-naphthyl methyl-phosphonate results in formation of l,r-binaphthyl. The reaction occurs only in compounds with at least two naphthyl substituents linked by an 0-P(0)-0 chain. Reaction involves intramolecular face-to-face dimerisation of the two naphthyl units within the radical cation (445), followed by elimination of the 1,1 -binaphthyl radical cation, which is subsequently reduced by the DCA radical anion. In a related reaction DCA-sensitisation of bis(3,4-methylenedioxy-phenyl) methylphosphonate in acetonitrile gives 2-(3,4-methylenedioxyphenyl)-4,5-methylenedioxyphenyl methylphosphonate whereas direct irradiation in methanol gives bis(3,4-methylenedioxy)biphenyl as an additional product. " ... 

Nitronium salts are capable to induce the OCA reaction via generation of aryl radical-cations, even with relatively electron-poor arenes, such as benzene [105]. Namely, NOBF4 in catalytic amount (1-5 mol%) efficiently catalysed the oxidative coupling reactions of polyalkoxybenzenes in dichloromethane (containing 20% trifluoroacetic acid) under exposure to air affording the corresponding biaryls in almost quantitative yields [105]. Finally, oxidative couplings of arenes can be accomplished under the classical Scholl reaction conditions [106]. For example, 1-ethoxynaphthalene (419) was coupled to binaphthyl 420 by reaction with anhydrous aluminum chloride and nitrobenzene (as oxidant) in 65% yield, Scheme 28. 

A large number of aromatic hydrocarbon radical anions has been reacted with Wurster s Blue-type radical cations, e.g. the radical anions of 1-phenylnaph-thalene, 8,8 -dimethyl-naphthalene, 1,1 -binaphthyl, p-terphenyl, chrysene, 1,2-dimethylchrysene [29]. They all represent energy-deficient systems, so that triplet-triplet annihilation had to be regarded as the mechanism for the production of the emitting singlet state. The quantum yields were in the range 10" to 10" Einstein/mol [29]. 

---