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isolated and fully characterized. Chromatographic analysis of the reaction mixture indicates that 12 is produced immediately upon addition of acetic acid to 11, whereas 8 is produced only upon warming the solution. The conversion of 11 to 12 may be formulated as an intramolecular Diels-Alder reaction of the protonated form of 11. The Diels-Alder reaction has been demonstrated with 11 itself, but it is slow in toluene at 110 °C.1 23456 The transformation of 12 into 8 is presumably a rr-cyclization of the prenyl double bond onto the immonium moiety of 12. It is noteworthy that the process is highly stereoselective with respect to the isopropenyl group and delivers 8 with the double bond situated only in the terminal position. We believe that a process such as this may be involved in the biosynthesis of the Daphniphyllum alkaloids.The total synthesis reported here is notable for its brevity and high yield; only nine laboratory operations are required from homogeranyl iodide, and the overall yield from this material is 44%. At the present time, we have prepared more than 3 g of 10 in this manner.

We report a highly efficient charge separation system, D-Pt-A, where D (triphenylamine) and A (naphthalenediimide) are bonded to the Pt moiety through highly twisted phenylene ethynylene linkages. The quantum yields for the formation of the charge-separated state were determined to be nearly unity. The lifetimes of D(+)-Pt-A(-) were approximately 1 micros at room temperature and much longer at low temperature. The spin-correlated radical ion pair was directly observed by means of time-resolved EPR spectroscopy.

A planar stable triphenylamine radical cation is a fascinating p-electron system that is potentially applicable to electronic and magnetic materials. Hellwinkel and co-workers synthesized an interesting compound 1, [1] from which the radical cation 1C+ was generated in concentrated sulfuric acid [1a] or by oxidation with lead tetraacetate in trifluoroacetic acid.[1c] The triphenylamine framework of 1C + is most likely planar. The dimethylmethylene bridges contribute to its stabilization; however, they disrupt the CT-type intermolecular interaction that is crucial for the construction of electronic and magnetic materials. To overcome this disadvantage and to improve stability, we designed a synthetic route to the new oxygenbridged analogue 2. [2,3] Quite recently, Livant and co-workers described a product fraction showing a molecular ion of m/z = 287 in the thermolysis of tris(2,6-dimethoxyphenyl)amine. They assumed the structure 2 for the MS peak. However, the compound showed no NMR spectroscopic signal.[4] Herein, we report the preparation, structures, and properties of the neutral 2 and the radical cation 2C+ .The synthesis of 2 is outlined in Scheme 1. Sequential aromatic nucleophilic substitution reactions of 2,6-difluoronitrobenzene with 2-bromo-3-methoxyphenolate and then with 2-bromo-3-fluorophenolate gave 4 (71 % yield in two steps). The reduction of 4 proceeded selectively in the presence of p-bromophenol (10 equiv) to avoid a competing reduction of aromatic bromide. Intramolecular cyclization of 5 was performed under Pd 0 -mediated cross-coupling reaction conditions [5] to afford 6 in 35 % yield. Treatment of 6 with BBr 3 gave 7 in good yield. Intramolecular nucleophilic substitution of 7 in DMF with K 2 CO 3 as a base proceeded efficiently under remarkably mild conditions to give the desired compound 2 in good yield. Compound 2 had a reversible oxidation wave at + 0.59 V versus SCE in DMF (SCE = saturated calomel electrode). The chemical oxidation of 2 was performed by using tris(p-bromophenyl)aminium hexafluorophosphate as an oxidant in methylene chloride. The salt 2CÀ can be recrystallized from acetonitrile/ diethyl ether. Figure 1 shows the molecular structures determined by Xray crystallographic analysis of 2 and 2C + .[6] The neutral compound 2 has a shallow bowl structure, whereas the radical cation 2C + has a planar structure. The CÀN bond lengths become shorter and the C-N-C bond angles approach 1208 in the radical cation 2C+ . The bond-length difference is in qualitative accordance with the HOMO shape of 2; that is, the C À N and C À O bonds have an antibonding nature in the HOMO.Triphenylamine radical cations without para substituents are generally unstable because of the large spin densities of Scheme 1. Reaction conditions: a) 2-bromo-3-methoxyphenol, NaH/ DMSO, 130 8C; b) 2-bromo-3-fluorophenol, NaH/DMSO, 130 8C; c) hydrazine hydrate, Pd/C, p-bromophenol/ethanol, reflux; d) NaOtBu, [Pd-(dba) 2 ], P(tBu) 3 /toluene, reflux; e) BBr 3 /CH 2 Cl 2 , À78 8C!room temperature; f) K 2 CO 3 /DMF, ...

We determined almost complete flagellin gene sequences of various Borrelia species and aligned them with previously published sequences. A neighbor-joining phylogenetic analysis showed that the genus Borrelia was divided into the following three major clusters: New World relapsing fever borreliae (BorreZia turicatae, Burreliu parkeri, and Borrelia hermsii), Old World relapsing fever borreliae (Borrelia crocidurae, Borrelia duttonii, and Borrelia hispanica), and Lyme disease borreliae (Borrelia burgdurferi sensu stricto, Borrelia garinii, and Borrelia afzelii). Agents of animal spirochetosis (Borrelia coriaceae and Borrelia anserina) and species of unknown pathogenicity (Borrelia rniyamotoi and Borrelia Zonestari) were related to relapsing fever borreliae. Although the Lyme disease borreliae, two related species (Borrelia japonica and Borrelia andersonii), and some newly described genomic groups (groups PotiB2, VS116, DN127, Hk501, and Ya501) were closely related to each other, each taxon formed an independent branch on the phylogenetic tree. The data obtained in this study indicate that the flagellin genes are useful in Borrelia taxonomy. To distinguish the Lyme disease borreliae from related organisms easily, we designed an oligonucleotide primer set for the flagellin gene and performed a PCR-restriction fragment length polymorphism (PCR-RFLP) analysis. The primer set amplified an approximately 580-bp DNA fragment that included species-specific restriction sites, and HapII, HhaI, CelII, HincII, or DdeI digestion of the product resulted in distinctively different PCR-RFLP patterns. The PCR-RFLP typing method which we developed should facilitate rapid identification of Lyme disease borreliae and related organisms obtained from biological and clinical specimens.

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Photoinduced charge separation of a phenothiazine–anthraquinone dyad 1 with a rigid bicyclo[2.2.2]octane spacer was investigated by means of picosecond and nanosecond transient absorption and time-resolved ESR spectroscopies. Irradiation of the anthraquinone chromophore in 1 produced the charge-separated (CS) state in THF. Time constants of the formation and the decay of the CS state were determined to be 1.3 ns and 1.0 µs, respectively. Time-resolved ESR showed spin-polarized all-emission signals due to the formation of the CS state via the triplet mechanism.