Tether length dependence

Scheme 6.15 Tether length dependence of half-rings (molecular weights relative to PS the intramolecular dimerization of templated standards).

At the same time, the stereoselectivity and stereodirection of the ISOC process substantially depend on the tether length (Scheme 3.141). 

At the same time, cycloaddition does not occur when the tether length is increased by one more atom (110). The stereoselectivity of cycloaddition depends on both the tether length (n = 1 or 2) and the configuration of the reacting C,C double bond, which was established in several reactions (110). 

The corresponding copper(I) adduct of pyridine functionalised carbene carrying only one pendant functional group shows interesting structural dependencies on the size of the wingtip group, the tether length and even the solvent used for crystallisation [26] (see... 

The coupling element H (r) in eqs. 4.63 and 4.64 falls off exponentially in the usual manner. Consequently, electrochemical rate coefficients are predicted to fall off exponentially with increasing tether length r, and this has been verified in several studies, with p values depending on the nature of the tether and generally falling in the range 0.5-l A e.g. Finklea et al., 1992 Smalley et al., 1995). There is some evidence that... 

Both reaction modes A and B have been observed for carbopalladations of methylenecyclopropane derivatives 59a,b with subsequent intramolecular nucleophilic trapping of the intermediate allylpallatium species in or IV, respectively, depending on the tether lengths between the methylenecyclopropane and the dimethyl malonate moieties. The same carbopalladations of unsubstituted methylenecyclopropane 43 (=60a) and pentyli-dene-cyclopropane (60b) with subsequent intermolecular trapping by carbon nucleophiles were found to generally proceed by mode B via intermediates II, V, IV to yield ringopening products 61 and 62, respectively (Scheme 16). 

For example, treatment of the aminals shown in eqs 32 and 33 with TMS-Br leads to piperdines with either exo- or endo-cyclic unsaturation depending on the tether length. Interestingly, the only reported products were the piperdines no pyrrolidine-derived compounds were observed even with tethers shorter than two methylene groups. 

TABLE 19.5 Quantum Yield Dependence on Tether Length and Flexibility... 

Hoveyda and coworkers [227] used a domino process to give chromanes 6/3-8 by treatment of 6/3-7 in the presence of ethylene. One of the first-generation Grubbs catalyst 6/3-9 and one of Blechert s [228] early examples allowed the synthesis of bicyclic compounds of different sizes, depending on the length of the tether thus, the reaction of 6/3-10 led to 6/3-11 using 30 mol% of the Schrock Mo complex 6/3-12. 

For the cyclization of the less nucleophilic sulfonamides, this conversion can only be achieved via this two-step protocol. The addition of I2 was highly regioselective, addressing the terminal C=C bond, whereas the second step could deliver several products including the SN2-substitution, SN2 -substitution and bimolecular double substitution products 297-299, depending on the length of the tether connecting the amine and the allene moiety [144, 145],... 

Marks et al. s organolanthanide catalysts show a strong dependence on the substitution of the allene [99]. Terminal allenes 144 with three carbons in the tether deliver the tetrahydropyridines 145. 1,2-Disubstituted allenes with the same length of the tether lead to the vinylpyrrolines 146 (Scheme 15.45). 

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