2- naphthyl groups

A similar but smaller intramolecular quenching effect was seen by Phillips and co-workers 44,4S) for 1-vinylnaphthalene copolymers incapable of excimer fluorescence. The monomer fluorescence lifetime of the 1-naphthyl group in the methyl methacrylate copolymer 44) was 20% less than the lifetime of 1-methylnaphthalene in the same solvent, tetrahydrofuran. However, no difference in lifetimes was observed between the 1-vinylnaphthalene/methyl acrylate copolymer 45) and 1-methylnaphthalene. To summarize, the nonradiative decay rate of excited singlet monomer in polymers, koM + k1M, may not be identical to that of a monochromophoric model compound, especially when the polymer contains quenching moieties and the solvent is fluid enough to allow rapid intramolecular quenching to occur. 

The phase-transfer benzylation of 2 with the catalyst (S)-12a having [1-naphthyl group on the 3,3 -position of the flexible biphenyl moiety proceeded smoothly at 0 °C to afford the corresponding alkylation product (R)-3 in 85% yield with 87% ee after 18 h. The origin of the observed chiral efficiency could be ascribed to the considerable difference in catalytic activity between the rapidly equilibrated, diaste-reomerichomo- and heterochiral catalysts namely, homochiral (S,S)-12a is primarily responsible for the efficient asymmetric phase-transfer catalysis to produce 3 with high enantiomeric excess, whereas the heterochiral (R,S)-12a displays low reactivity and stereoselectivity. 

In another study,4 the substituents on the phosphoramidite ligand on the [IrCODClh catalyst were altered from aryl groups to 1-naphthyl groups. This led to higher yields (>94%), and greater regio- and enantio-selectivities in the 5 2 reaction between several substituted allylic carbonates and amines or phenoxides. The S 2 /S 2 product ratios were >91 9 with the new catalyst. 

Absolutely no excimer has been detected when 1-naphthyl groups are linked to a helical polypeptide in a similar manner [49, 50]. The stabilization energy of naphthyl excimers may be too small to hold excimer configurations. 

Sequential treatment of 3-acetylthiazolidine-2-thione (1055) with stannous trifluoro-methanesulfonate, diamine 1057, and methyl pyruvate results in the formation of adduct 1058 with S5Vo ee. The 1-naphthyl group on the pyrrolidine system is essential to ensure high asymmetric induction. Other groups such as cyclohexyl, phenyl, 2,6-xylyl, or 2-naphthyl... 

The best results were obtained with 1-naphthyl-TADDOL 2a, but yields and ee values depended critically on the structure of the aldehyde although an excellent y-selectivity was always observed. In this case a ti-ti interaction between the electron-rich 1-naphthyl group and the electron-poor carbonyl group should further stabilize the hydrogen-bonded aldehyde, leaving the Re face accessible to nucleophile. 

The allyl transfer is highly regiospecific (Scheme 5.12) [12b,c]. The allyl transfer from linear alcohol 3 to 1-bromonaphthalene (Np represents the 1-naphthyl group hereafter.) affords the corresponding branched product. It is worth noting that the... 

In 1995 Hirama and coworkers [16] reported an asymmetric Baylis-Hillman reaction catalyzed by chiral 2,3-disubstituted DABCO derivatives under increased pressure (Scheme 21.2a). Hirama observed an enhancement of both reaction rate and enantioselectivity for the reaction of 4-nitrobenzaldehyde with MVK under 5 kbar. At atmospheric pressure the reaction proceed very slowly (3 weeks) with low enantioselectivity (12-15% ee). The best results in terms of yield and enantioselectivity (up to 47%) were obtained with chiral DABCO catalyst bearing benzyl or 1-naphthyl groups. This is the first example of an organocatalytic reaction demonstrating that an increase in pressure can significantly enhance the enantioselectivity (e.g., from 12% to 47%). 

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