To compare the crystalline-state conformations of MαNP acid esters with those existing in the solution state, X-ray crystallographic analyses of 22 MαNP esters and two MαNP acids were carried out. It was found that all 27 conformers observed in the solid state have structures in which the 2-CH 3 group and the 2Ј-H of the naphthyl group are synperiplanar and are almost always located in the same plane. In addition, the CH 3 -O7-C2-C1 moiety in all cases has an antiperiplanar structure within the MαNP plane. From further analyses, 22 conformers adopt the so-called syn structure, in which the O7-C2-C1-O6 moiety is synperiplanar. On the other hand, the remaining five conformers have the so-called anti structure. With regard to the rotational conformation around C1ЈЈ-O5, all conformers have structures similar to the synperiplanar conformation. In the so-called syn conformers, the interatomic distance d(H8Ј-O6) is distributed between 2.48 Å and 2.96 Å, while the distance d(H8Ј-O7) varies between 2.26 Å and 2.56 Å, indicating the weak bifurcated hydrogen

The MαNP acid method has been applied to racemic aliphatic acetylene alcohols in order to simultaneously prepare enantiopure alcohols and to determine their absolute configurations by 1 H NMR anisotropy. Racemic acetylene alcohols 6-8, 11, and 20 were esterified with MαNP acid (S)-(+)-1 to yield diastereomeric MαNP esters which were efficiently separated by HPLC on silica gel with separation factors α in the range 1.60-1.93. The 1 H NMR anisotropy factors ∆δ [= δ(2nd fr.) -δ(1st fr.)] were calculated from the data of the first-(22a-

A novel methodology using a chiral molecular tool of MalphaNP acid (1), 2-methoxy-2-(1-naphthyl)propionic acid, useful for preparation of enantiopure secondary alcohols and determination of their absolute configurations by the (1)H NMR anisotropy method was developed; racemic MalphaNP acid (1) was enantioresolved with (-)-menthol, and the enantiopure MalphaNP acid (S)-(+)-(1) obtained was allowed to react with racemic alcohol, yielding a mixture of diastereomeric esters, which was clearly separated by HPLC on silica gel. By applying the sector rule of (1)H NMR anisotropy effect, the absolute configuration of the first-eluted MalphaNP ester was unambiguously determined. Solvolysis or reduction of the first-eluted MalphaNP esters yielded enantiopure alcohols.

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Photoinduced electron transfer (PET) followed by back electron transfer (BET) reactions of 1,2-bis(a-styryl)benzenes 1,g enerates o-quinodimethane derivative 2 via the corresponding radical cation 2 · + .T his process serves as af acile methodt of orm o-quinodimethane intermediates. The intermediacy of 2 · + and 2 werec onfirmed by using various spectroscopicm ethods and trapping reactions with 3 O 2 and dienophiles. Kinetic analysisu sing nanosecond time-re-solved absorption showed that 2 · + was transformed to 2 via aB ET process, in which the decay of 2 · + and rise of 2 have almostt he same rate constants of k DECAY = 5.6 10 5 s À1 and k RISE = 5.9 10 5 s À1 ,r espectively.T he net BET rate constant evaluated by using Marcus theory is much faster than these experimental values, owing to the reduction based on diffusion.[a] Prof.form (M · + + +A · )a nd thes econdE Ti n( D + +M · + )f orms (D · + + +M). Ther esulting long distance betweenD · + andA · effectivelyp reventsf ormationo f[ D · + //A · ], thereforet he lifetime of D · + is substantially extended.I nt erms of analyzingt he BETp rocess, the most importanti nt hise fforti sB ET between( D · + + +A · ), whichi s formed in theP ET reactionss hown in Scheme 1b and1 c. As showni nS cheme1d, ther atec onstant (k BET )i sd efined fort he BETreactioni nt he encounterc omplex [D · + //A · ] EC that relatest o theassociation anddissociationof(D · + + A · ).Uncharged organic sensitizers, such as 9,10-dicyanoanthracene (DCA, Figure 1) and 1,4-dicyanonaphthalene (DCN), are conventional. Typical cationic sensitizers such as N-methylquinoliniumt etrafluoroborate (NMQ + BF 4 À ), [6] 2,4,6-triphenylpyrylium tetrafluoroborate( TPP + BF 4 À ), and N-methyl-9-mesitylacridinium perchlorate (Mes-Acr + ClO 4 À ,F ukuzumip hotocatalyst 7 ) can promote reactions of free D · + .R ecently,o rganometallic complexes,s uch as Ru(bpy) 3 2 + (Cl À ) 2 and fac-Ir(ppy) 3 ,h ave also been used in organic synthesis. [8] Upon excitation by visible light, these complexes undergo intersystem crossing to form long-lived triplet excited states.T he long lifetime induces ah igh possibility of collision with D, while the triplet state at alow energy level results in relatively low oxidation ability. g-Irradiationi naspecific solvent can also induce ET without any sensitizer and is often used forspectroscopic measurements.Kinetic analysiss uch as Stern-Volmer analysis is ap owerful tool to examine the synthetics tudy on aP ET reaction. When using an on-fluorescents ensitizer,l aser flash photolysis (LFP) provides informationa bout the formation and decay of D · + (Figure 2a). However, information on the recovery of Db yB ET,

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