On the radical Brook and related reactions: an ab initio study of some (1,2)-silyl, germyl and stannyl translocations

Schiesser, Carl H.; Styles, Michelle L.

doi:10.1039/a702587d

Cited by 44 publications

(47 citation statements)

References 28 publications

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“…Not only were mechanisms involving both frontside and backside attack found to be mechanistically feasible, the energy barriers for both pathways are approximately equal 44 . Not unexpectedly, the transition states (52) for backside attack prefer to adopt collinear arrangements of attacking and leaving radicals, while the transition states (53) for frontside attack resemble those located in an earlier study involving 1,2-silyl, germyl and stannyl group migrations between carbon centres, or between carbon and either nitrogen or oxygen 45 . Values of r 1 (Scheme 10) for reactions involving attack of silyl radical (X D Si) lie between approximately 2.5Å (Y D Si) and 2.8Å (Y D Sn), while CCSD(T)/DZP//MP2/DZP calculated energy barriers for reactions involving silyl radical lie in the range 40 -65 kJ mol 1 and depend on the nature of the leaving radical and the heteroatom undergoing attack.…”

Section: Theoretical Studiesmentioning

confidence: 94%

Silyl Radicals

Chatgilialoglu

Schiesser

2009

Patai's Chemistry of Functional Groups

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Section: Theoretical Studiesmentioning

confidence: 94%

Silyl Radicals

Chatgilialoglu

Schiesser

2009

Patai's Chemistry of Functional Groups

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“…early, transition state with a preferentially collinear geometry of the [O-H-C] entity Scheme 47 A radical version of the Brook-rearrangement. [166][167][168][169][170] has been derived from molecular orbital calculations. 172 The rate of hydrogen atom abstraction correlates with C-H bond strengths (Table 3).…”

Section: Hydrogen Abstractions: Remote Functionalizations and Subsequmentioning

confidence: 99%

Selectivity in the Chemistry of Oxygen-Centered Radicals - The Formation of Carbon-Oxygen Bonds

Hartung¹,

Gottwald²,

Špehar³

2002

Synthesis

180

104

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In recent years, powerful new methods for the generation of alkoxyl radicals under mild and neutral conditions have been developed. This progress has led to a thorough investigation of most O-radical elementary reactions. Today, sufficiently reliable thermodynamic and kinetic data are available either from experimental or from theoretical studies in order to predict alkoxyl radical reactivities and selectivities in synthesis. For instance, alkoxyl radicals readily add to carbon-carbon and carbon-nitrogen double bonds. Due to generally low activation barriers and strongly negative reaction enthalpies, inter-and intramolecular addition reactions proceed under kinetic control and are associated with high rate constants. Nevertheless, intramolecular 5-exo-trig additions, i.e. cyclizations, proceed with an astonishing degree of diastereoselectivity and often provide complementary selectivities if compared to commonly used methods such as the bromine cyclization of alkenols. Therefore, several useful applications of O-radical cyclizations in the synthesis of functionalized tetrahydrofurans have been discovered in the last few years. A second major reaction channel of alkoxyl radicals is associated with the homolysis of a b-CC bond. This fragmentation proceeds under thermodynamic control and affords a carbonyl compound besides an alkyl radical from the starting alkoxyl radical. Regioselectivities for CC bond homolysis may be predicted by considering strain release (cyclic carbon framework) and the stability of the newly formed carbon radical (cyclic and open chain carbon skeletons). The third major group of alkoxyl radical-based transformations are connected with homolytic substitutions such as intramolecular 1,5-hydrogen shifts which have been applied with considerable success to remote functionalization reactions. In view of the diversity of alkoxyl radical reactions it is the aim of this review to organize basic principles of this type of chemistry and to present its latest useful application in organic synthesis.

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“…For this reason, we initiated ab initio studies of the thermal rearrangement reactions of α‐silylalcohols 2, silylmethanol, and 1‐silylprop‐2‐en‐1‐ol. The results show that as compared with the rearrangement under strong base 3–9 and peroxide‐initiating 10–18 conditions, two dyotropic 19 rearrangement reactions may occur when α‐silylalcohols are heated. One is via the Brook rearrangement reaction, where the silyl group migrates from carbon atom to oxygen atom coupled with a simultaneous migration of a hydrogen atom from oxygen atom to carbon atom passing through a double three‐membered ring transition state, forming alkyloxysilane.…”

Section: Introductionmentioning

confidence: 96%

Theoretical study of thermal rearrangements of α‐silylalcohols: Effects of substituents attached to the silicon atom on the reactions

Feng

2006

Int J of Quantum Chemistry

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ABSTRACT:To investigate the effects of substituents attached to the silicon atom on the thermal rearrangement reactions of ␣-silyl alcohols, the thermal rearrangement reactions of dimethylsilyl methanol (CH 3 ) 2 SiHCH 2 OH and vinylsilyl methanol CH 2 ACHSiH 2 CH 2 OH were studied by ab initio calculations at the G3 level. Geometries of various stationary points were fully optimized at the MP2(full)/6-31G(d) and MP2(full)/6-311G(d,p) levels, and harmonic vibrational frequencies were calculated at the same levels. The reaction paths were investigated and confirmed by intrinsic reaction coordinate (IRC) calculations at the MP2(full)/6-31G(d) level. The results show that two dyotropic reactions could occur when (CH 3 ) 2 SiHCH 2 OH or CH 2 ACHSiH 2 CH 2 OH is heated. One is Brook rearrangement reaction (reaction A), and the dimethylsilyl or vinylsilyl groups migrates from carbon atom to oxygen atom coupled with a simultaneous migration of a hydrogen atom from oxygen atom to carbon atom passing through a double three-membered ring transition state, forming dimethylmethoxylsilane (CH 3 ) 2 SiHOCH 3 or methoxylvinylsilane CH 2 ACHSiH 2 OCH 3 ; the other is a hydroxyl group migration (reaction B) from carbon atom to silicon atom, coupled with a simultaneous migration of a hydrogen atom from silicon atom to carbon atom, via a double three-membered ring transition state, forming trimethylsilanol (CH 3 ) 3 SiOH or methylvinylsilanol CH 3 SiH(OH)CHACH 2 . The G3 barriers of the reactions A and B were computed to be 312.8 and 241.4 kJ/mol for (CH 3 ) 2 SiHCH 2 OH, and 317.6 and 233.7 kJ/mol for CH 2 ACHSiH 2 CH 2 OH, respectively. On the basis of the MP2(full)/6-31G(d) optimized parameters, vibrational frequencies, and G3 energies, the reaction rate constants k(T) and equilibrium constants K(T) were calculated using canonical variational transition state theory (CVT) with centrifugal-dominant smallcurvature tunneling (SCT) approximation over a temperature range of 400 -1800 K. The influences of methyl and vinyl groups attached to the silicon atom on reactions are discussed.

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On the radical Brook and related reactions: an ab initio study of some (1,2)-silyl, germyl and stannyl translocations

Cited by 44 publications

References 28 publications

Silyl Radicals

Silyl Radicals

Selectivity in the Chemistry of Oxygen-Centered Radicals - The Formation of Carbon-Oxygen Bonds

Theoretical study of thermal rearrangements of α‐silylalcohols: Effects of substituents attached to the silicon atom on the reactions

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