Tethered reactions

Dell C. P. Cycloaddition in Synthesis Contemporary Organic Synthesis 1997 4 87 Keywords natural products, metal catalyzed, asymmetric reactions, Ionic reactions, transannular reactions, tethered reactions, tandem reactions, benzo-qulnones, quinodimethanes, hefero-Dlels-Alder reactions... 

Bols M., Skrydstrup T. SiBcon-Tethered Reactions Chem. Rev. (Washington, D. C.) 1995 95 1253-1277... 

Another strategy to control the regio- and stereochemistry of cycloaddition is a silicon-tethered reaction, as discussed in the section of nitronates (Section 8.2.3) (Eq. 8.65).100... 

Scheme 20 Side-arm protein tethering. Reactions of biotin, iipoate, and coenzyme A to provide proteins with reactive handies for biosynthetic pathways.

Despite the development of various intermolecular radical addition methods, those studies have rarely accommodated additional functionality, our discovery of the manganese-mediated photolysis conditions notwithstanding. Prior to that discovery, we began to elaborate an alternative strategy which employs temporary tethers ([115, 116] reviews of silicon-tethered reactions [117-120]) (silyl ether or acetal linkages) linking radical and acceptor. In this scenario the C-C bond is constructed via cyclization, in which internal conformational constraints can control diaster-eoselectivity. The tether itself would be converted to useful functionality upon cleavage, and once the tether is cleaved the net result may be considered as formal acyclic stereocontrol. ... 

For a review on silicon-tethered reactions, Bols, M. Skrydstrup, T. Chem. Rev. 1995,95,1253. 

Bols, M., Skrydstmp, T. Silicon-Tethered Reactions. Chem. Rev. 1995, 95,1253-1277. 

The excellent ability and the wide applicability of the PD-tethered reaction have thus established a handy diastereo-differentiating reaction for the preparation of optically active compoimds. However, the outstandingly high stereo-control in this system is not explained by a conventional mechanism. The chiral PD-tether part has only two methyl groups and leads to a flexible medium ring in the transition states, where the methyl groups are not expected to introduce enough steric-repulsion nor structural strain to perform strict stereo-... 

Quantitative anaiysis of template effects in tethered reactions... 

Tethered reactions can be regarded as linear templated systems in which the template-substrate binding is infinitely strong. The template efficiency is therefore defined simply by the effective molarity for the intramolecular reaction the rate enhancement becomes greater than 2 when [S]q < EM, and becomes infinite at infinite dilution. 

Attention was then directed towards the development of a one pot procedure. The success of the tethering reaction with NIS indicated a reactivity differential between the enol ether and the anomeric thiophenyl group. Choice of solvent proved to be crucial, with 1,2-dichloroethane giving the best results. 

A general review has been published on silicon-tethered reactions with parts devoted to the preparation of branched-chain sugars (including nucleosides), through the addition of radicals generated from (bromomethyl)silyl ether tethers to double bonds or by the addition of radicals generated from phenyl selenides onto allylsilyl ether tethers. ... 

For a review on temporary silicon-tethered reactions, see (a) Bols, M. and Skrydstmp, T. (1995) Chem. 

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