Y cyclic

Delpuech J-J, Lambert JB, Takeuchi Y. Cyclic Organonitrogen Stereodynamics, VCH Publishers, New York, 1992. 

A 1,6-silyl migration from O to O was observed in the reactions of 3, 5 -cyclic dis-iloxanyl 0-uridine derivatives 331 with triflic anhydride which give quantitatively the 2 ,y-cyclic disiloxanyl 0-uridine derivatives 332 (equation 203)469,470. 

Rothenberg, G., Sasson, Y. Cyclic vs. acyclic allylic hydrogen abstraction an entropy motivated process Tetrahedron 1998, 54, 5417-5422. 

Optically active C synthons are obtained by stereoselective hydrogenation of methyl-substituted pentadien-l-ols with baker s yeast. They represent useful building blocks for the synthesis of <5- and y-cyclic ethers or lactones37. 

Yokoyama, K. Kayanuma, Y. Cyclic voltammetric simulation for electrochemically mediated enzyme reaction and determination of enzyme kinetic constants. Anal Chem. 1998, 10, 3368—3376. 

Yokoyama, Y., Miyasaka, M., Uchida, S., and Yokoyama, Y, Cyclic fulgenates. Enlargement of quantum yields of coloring reaction of photochromic fulgenates, Chem. Lett., 479,1995. 

Allemand P-M, Koch A, WudI F, Rubin Y, Diederich F, Alvarez M M, Anz S J and Whetten R L 1991 Two different fullerenes have the same cyclic voltammetry J. Am. Chem. Soc. 113 1051-2... 

Y. Wang and K. Kuczera. Molecular dynamics simulations of cyclic and linear DPDPE Influence of the disulfide bond on peptide fiexibility. J. Phys. Chem., 100 2555-2563, 1996. 

Flow chart showing the design of novel orally active HIV-1 protease inhibitor. (Figure adapted from Lam P K ]adhav, C E Eyermann, C N Hodge, Y Ru, L T Bacheler, ] L Meek, M ] Otto, M M Rayner, Y N V /ong, ang, P C Weber, D A Jackson, T R Sharpe and S Erickson-Viitanen 1994. Rational Design of Potent, able. Nonpeptide Cyclic Ureas as HIV Protease Inhibitors. Science 263 380-384.)... 

The addition of large enolate synthons to cyclohexenone derivatives via Michael addition leads to equatorial substitution. If the cyclohexenone conformation is fixed, e.g. as in decalones or steroids, the addition is highly stereoselective. This is also the case with the S-addition to conjugated dienones (Y. Abe, 1956). Large substituents at C-4 of cyclic a -synthons direct incoming carbanions to the /rans-position at C-3 (A.R. Battersby, 1960). The thermodynamically most stable products are formed in these cases, because the addition of 1,3-dioxo compounds to activated double bonds is essentially reversible. 

Cycloalkene (Section 5 1) A cyclic hydrocarbon characterized by a double bond between two of the nng carbons Cycloalkyne (Section 9 4) A cyclic hydrocarbon characterized by a tnple bond between two of the nng carbons Cyclohexadienyl anion (Section 23 6) The key intermediate in nucleophilic aromatic substitution by the addition-elimination mechanism It is represented by the general structure shown where Y is the nucleophile and X is the leaving group... 

In the X- and y-directions (Figure 49.5b), an ion trajectory is more difficult to visualize. It is essentially the sum of two main effects one a simple oscillation caused by the rapid cyclic alternations of the RF field (Figure 49.5c), the other a more complicated drift or guided motion due to the inhomogeneity of the RF field within the space between all four rods. 

The only clearly defined crystalline compositions are three forms of phosphoric acid and hemihydrate, pyrophosphoric acid, and crystalline P O q. The phosphoric acids obtained in highly concentrated solutions or by mixing phosphoric acid with phosphoms pentoxide are members of a continuous series of amorphous (excluding [Y OO]) condensed phosphoric acid mixtures. Mixtures having more than 86% P2O5 contain some cyclic metaphosphoric... 

We present here examples of this condensation with an aromatic aldehyde and a cyclic ketone. Both of these examples are useful because, although other methods are available for their preparation, problems often attend these syntheses. In the synthesis of cyclohexy11deneaceton1tr11e, for example, the standard method results exclusively In the g.y-lsomer and none of the a,g-Isomer. In Part A of this procedure, cyclohexanone Is condensed with acetonitrile to give predominantly the conjugated Isomer (80-83%) whicfi is then separated from the nonconjugated isomer by selective bromination. 

The mechanism of this reaction has been studied by several groups [133,174-177]. The consensus is that interaction of ester with the phenolic resole leads to a quinone methide at relatively low temperature. The quinone methide then reacts rapidly leading to cure. Scheme 11 shows the mechanism that we believe is operative. This mechanism is also supported by the work of Lemon, Murray, and Conner. It is challenged by Pizzi et al. Murray has made the most complete study available in the literature [133]. Ester accelerators include cyclic esters (such as y-butyrolactone and propylene carbonate), aliphatic esters (especially methyl formate and triacetin), aromatic esters (phthalates) and phenolic-resin esters [178]. Carbamates give analogous results but may raise toxicity concerns not usually seen with esters. 

Fig. 1.2 shows a gas turbine power plant operating on a closed circuit. The dotted chain control surface (F) surrounds a cyclic gas turbine power plant (or cyclic heat engine) through which air or gas circulates, and the combustion chamber is located within the second open control surface (Z). Heat (2b is transferred from Z to Y, and heat (2a is rejected from Y. The two control volumes form a complete power plant. 

For a cyclic gas turbine plant in which fluid is circulated continuously within the plant (e.g. the plant enclosed within the control surface Y in Fig. 1.2), one criterion of performance... 

Polyfluorinated a-diketones react with 1,2-diainino compounds, such as ortlio-phenylenediamine, to give 2,3-substituted quinoxalmes [103] Furthermore, the carboxyl function of trifluoropyruvates offers an additional electrophilic center. Cyclic products are obtained with binucleophiles [13, 104] With aliphatic or aromatic 1,2-diamines, six-memhered heterocycles are formed Anilines and phenols undergo C-alkylation with trifluoropyruvates in the ortho position followed by ring closure to form y-lactams and y-lactones [11, 13, 52, 53, 54] (equation 23). 

At least eight further cyclic modifications of sulfur have been synthesized during the past 25 y... 

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