Relative reactivity values

Comparison of the Relative Reactivity Values Obtained by Different Methods in the Reeslerification of Esters... 

Competition Experiments of Ley Ley examined product distributions to obtain relative reactivity values (RRVs) for both rhamnose and mannose sugars with benzyl, 3,4-cyclic diacetals, and benzoyl groups. Using a limiting amount of acceptor (1 equiv), two donors were added in excess (2 equiv each), followed by the addition of activator (NIS/TfOH, 2 equiv) (Scheme 11.13). After quenching the reaction, the product distribution was analyzed by -NMR. 

Scheme 11.16 Monitoring the relative reactivity values of four reference molecules.

Scheme 11.17 Tabulation of the relative reactivity values of various carbohydrates.

Unlike the other N5 modifications described previously, a 5-azido thioglycoside was found to be less reactive than the simple amide as is clear from the measured relative reactivity values (RRVs) (Fig. 5.4) [59], However, it was subsequently reported by Teruaki Mukaiyama and coworkers that a 5-azido sialyl fluoride was more reactive than both the corresponding acetamide and the V,V-diacctyl derivatives toward activation with the combination of SnCl4 and AgB(C6F5)4, although this may be a consequence of the differing anomeric stereochemistries employed [60],... 

SCHEME 12.12 Wong s synthesis of Globo-H. CIBn, o-chlorobenzyl NBz, p-nitroben-zoyl PMP, p-methoxyphenyl RRV, relative reactivity value. 

SCHEME 14.2 Synthesis of lipid IV by Wong, Cheng, and coworkers. ClAc, chloroacetyl NIS, /V-iodosucci n i mide Phth, phthaloyl PyBOP, benzotriazol-l-yl-oxytripyrrolidinophos-phonium hexafluorophosphate RRV, relative reactivity value TBAF, tetrabutylammonium fluoride TBS, fert-butyldimethylsilyl Tf, trillyl TMS, trimethylsilyl Tol, 4-tolyl. 

If the relative reactivity value is obtained using the method of competitive reactions, the reactivity is given by the ratio of the rate equations of type (3) for both compounds (74) the denominators of the fractions cancel out ... 

It should be mentioned that all these experiments were earned out independently (on different catalyst samples or on the same sample which was reactivated by treatment under air flow at 500°C overnight). Hence the relative reactivity values seem reliable since for instance the reactivity ratio between iodobenzene and chlorobenzene deduced from Experiments 2 and 5 is the same as the one obtained by multiplying the reactivity ratio between iodobenzene and bromobenzene (Experiments 3 and 6) by the reactivity ratio between bromobenzene and chlorobenzene (Experiments 1 and 4). 

The relative reactivity values for a number of relatively simple olefins ... 

The relative reactivity values that have been derived from the extensive research with these numerous olefins indicates that oxygen atoms are electrophilic. While not quite as selective as bromine atoms, the oxygen atom is not nearly as reactive and non-specific as one might possibly expect when the general character of oxidatioA is considered. Inspection of Table 22 indicates that isobutene is anomolous in its reactivity, if the value of Cvetanovic or the lower limit of the range noted by Herron and Huie is accepted, so there is obviously more work needed. 

We have measured the rate of nitration of nitrobenzene, m-dl-nltrobenzene, and dlnltrotoluenes by conventional methods. The rate data obtained were shown In Tables XVIII and XIX. For comparison, both relative reactivity values calculated from the separate rate determinations and those from competitive reactions are also shown In these tables, Indicating that the relative reactivity... 

Relative Reactivity Values (RRVs). which are the experimentally determined values relating the reactivities of the BB s to the stamdard sugar... 

Figure 5. Wong s One-Pot synthesis of Globo H. Numbers in parentheses are relative reactivity values (RRVs).

Keywords Carbohydrates Oligosaccharides One-pot OptiMer Relative reactivity values Thioglycosides... 

Fig. 6 The relative reactivity values (in parentheses) of sialic acid thioglycosides...

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