Reactivity yield

Irradiation of the bis-alkene 210 brings about the formation of the bishomocubane 211 in good yield98. The triene 212 is of interest and has been shown to be photochemically reactive, yielding the adduct 213 on irradiation. Several approaches to 212 have been reported over the years. One such approach follows the path of photocyclization of 214 to yield 215 that can be converted to the desired product 21299. A variety of sensitizers can be used for the excitation of alkenes to bring about the (2 + 2)-cycloaddition. Commonly, acetone has been used but, in at least one case, the formation of the cage compound 216 from the diene 217, tetraphenylporphine has been found to be of use100. 

Of particular interest are cases in which substituents are present in ortho positions to the reacting methyl group. Apart from o-chloro-substituted derivatives, those with methoxy, carbonamido, sulfonamido, and phenylsulfonyl groups have been reported to undergo reaction.68 The 2-(3-chloro-4 methyIphenyl)-5-methoxybenzotriazole (163) has been found to be particularly reactive, yielding, with Schiff s base 98, the stilbene 164.54... 

Conjugate addition of RMgX to enones.1 This complex can serve as a catalyst for this reaction. The related complex in which one chlorine is replaced by methoxy is somewhat more reactive. Yields of adducts are similar to those obtained by use of 1 equiv. of trialkyIzincates. 

Cyanide ion reacts by the SN2 mechanism and aprotic solvents are often employed to increase its reactivity. Yields of substitution products are excellent when the leaving group is attached to a primary carbon. Because of competing elimination reactions, yields are lower, but still acceptable, for secondary substrates. As expected for an SN2 process, the reaction does not work with tertiary substrates. Substitution with cyanide ion adds one carbon to the compound while also providing a new functional group for additional synthetic manipulation. Some examples are given in the following equations ... 

The polystryrene-bound biguanides were checked under exactly the same conditions and exhibited excellent catalytic properties (Table 1). The immobilization of the biguanide units induced only a very limited decrease in the reactivity. Yields above 90% were obtained in less than 15 mn. The yields of methyl esters are above 94% even before 15 mn reaction time. 

On the other hand, heavier rare gases are not acting as effectively in removing energy from the internally hot, nascent, molecular products. The yield of stable molecular products is favored in lighter rare gases (cf. Fig. 14) where the reactive yield is plotted for Ne and Ar rare gas clusters on a reduced energy scale. 

Due to the mild experimental conditions (room temperature to 60 °C and gentle mechanical shaking), the recycling of the supported reagent could easily be achieved without significant loss of reactivity (yields decreased from 95% to 90% over five cycles) and with a remarkable control of tin contamination <5 ppm. ... 

The first studies examined refer to the transfer of classic CM protocols with Grubbs I and II generation catalysts 64 and 65 in two ionic liquids, [bmim][PF6] and [bmim][BF4]. Compared to the same reactions in CH2CI2 significant enhancements in the reactivity, yield and reaction rate were achieved. The advantage of using ILs is that the catalyst/IL system could be simply recovered and reused for at least four cycles with only a small drop in activity. 

For electron-capture detection, pentafluorobenzyloxyamine has been described [230]. 2-Chloroethoxyamine [231] has been recommended as an oximating agent of high reactivity, yielding chlorooximes the chloro-compound mass-spectral pattern is alleged to be helpful in identification. 

I rodiicl type hydrogens reactivity yield yield... 

A calculation of a versus total added carbonate, assuming negligible bicarbonate reactivity yields a kjc (TC = total carbonate) of 3.57 z 10 M"1 s with a regression coefficient, r 0.74. Adding a total bicarbonate reactivity term (kxg) equal to l/30th of the carbonate reactivity, we calculated that kyc = 3 30 z 10 s ... 

The ylide obtained from dichlorodifluoromethane or dibromodifluoromethane and P(NMea)3 in triglyme is stable but reactive, yielding for example the olefin PhCMerCFa (68 %) with acetophenone after ageing for 300 h. Heptafluoropropyl-... 

In the presence of 3-HQD or DABCO, the MBH reaction between resin-bound acrylate and various aldehydes with different reactivities yielded allylic alcohols 69 and 70 in moderate to excellent yields by simply varying the base or the reaction time, " which led to a combinatorial synthesis of substituted racemic 3-hydroxypropionamides, amino alcohols " or arylpropanolami-nes " via the treatment with amines and the use of different cleavage methods (Scheme 2.30). 

The surface of iron oxides contain OH groups that are reactive, yielding marked acid-base behavior, thus a rather strong pH dependence of the surface charge iron oxides are major components of variable charge soils, as discussed in Chapter 5. These surface groups react with ions, binding specifically both anions and cations. These features are discussed in Section 9.7. 

The mechanism of this series of reactions involving dodecyl mercaptan chain-transfer during a high pH polymerization was elucidated using radio-sulfur-tagged dodecylmercaptan (18). The use of multiple chain-transfer agents of different reactivities yielded polymer of more uniform structures (19). 

The reactivity of the catalysts increases with greater atomic number. An enhanced reactivity yields a polymer with higher molecular weight, but its weight distribution broadens. An example is given in Table 5. 

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