Experiment regioselectivity factor

The regioselectivity of cof r carbenoids (and of most carbencs) is typical for an electrophilic species which preferentially attacks the electron-rich sites of the molecules. For example, competitive experiments with olefins bearing different substituents give a mixture of cyclopropanes, which is the result of both electronic and stcric control of the reaction with the electronic factors being often predominating. 

Competition experiments between two ir-bonded nucleophiles within the same molecule were studied in an attempt to identify reaction parameters and factors responsible for regioselectivity. These experiments, summarized in heme 12, demonstrated that the dithioacetal (initiating carbocation) is in competition with two nucleophilic functional groups within the same molecule, a silyl enol ether and a vinylsilane. In this instance, when the thioacetal (29) was treated with DMTSF, complete chemoselectiv-... 

This unexpected finding encouraged them to further explore the factors that control the regioselectivity in this AFC reaction. Further experiments were carried out to disclose a clear picture of the binary acid catalysis. Besides the critical role of such binary acids in stereocontrol, the judicious selection of chiral phosphoric acid, Lewis acid and combination is essential... 

The factors that control regioselectivity of palladium-catalyzed allylic substitutions have been the subject of numerous studies. Experiments that reveal the effects of both symmetric and unsymmetric ancillary ligands on this regioselectivity have been reported, along with experiments that have revealed effects of the type of nucleophile and the effects of basic additives. The following section describes some of this work on palladium-catalyzed processes. 

This chapter will discuss the factors affecting the reaction regioselectivity of several alkenyl substrates and the related mechanistic aspects arising fi-om in situ IR spectroscopic studies and deuterioformylation experiments. 

Coote ML. Radical reactivity by computation and experiment. In Matyjaszewski K, ed. Polymer Science A Comprehensive Rference. Amsterdam Elsevier BV 2012 3—58. Tedder JM. Which factors determine the reactivity and regioselectivity of free radical substitution and addition reactions Angew Chem Int Ed. 1982 21 401-410. 

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