Radical-catalyzed rearrangement of trisilanethiols

Pitt, Colin G.; Fowler, Mary S.

doi:10.1021/ja01009a062

Cited by 27 publications

(9 citation statements)

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“…Indeed, as expected, structures of C 2 symmetry (10) were located on the C 6 H 12 X (X ) Cl, Br, I) potential energy surfaces at both UHF and MP2 levels with all basis sets used in this study. Structures (10) proved to correspond to transition states for 1,6-halogen transfers in the 6-halo-1-hexyl radicals (7). Structures (10, X ) Cl) of C s symmetry were also located at the UHF/ 3-21G ( * ) and UHF/6-311G** levels of theory; these proved to correspond to second-order saddle points (two imaginary frequencies) with one vibrational mode corresponding to the collapse to the corresponding C 2 transition state.…”

Section: 6-translocations In 6-halo-1-hexyl Radicalssupporting

confidence: 76%

“…We began our computational study by attempting to locate the anticipated C 2 symmetric transition structures involved in the 1,6-translocation of the halogen atom in the 6-chloro-1-hexyl, 6-bromo-1-hexyl, and 6-iodo-1-hexyl radicals (7). Indeed, as expected, structures of C 2 symmetry (10) were located on the C 6 H 12 X (X ) Cl, Br, I) potential energy surfaces at both UHF and MP2 levels with all basis sets used in this study. Structures (10) proved to correspond to transition states for 1,6-halogen transfers in the 6-halo-1-hexyl radicals (7).…”

Section: 6-translocations In 6-halo-1-hexyl Radicalsmentioning

confidence: 91%

“…Stannyl groups appear also to undergo intermolecular translocation chemistry; Scaiano reported that tert-butoxyl radicals undergo intermolecular homolytic substitution at the tin atom in hexabutylditin. 9 In addition to several reports involving 1,2-silyl and germyl shifts, 10 intramolecular homolytic group transfers involving silicon, germanium, and tin have been put to good use by Davies and co-workers 11 as well as by Kim and his associates (Scheme 2). 12 There also appear to be several early reports of 1,2 migrations of halogen, 13 the Nesmeyanov rearrangement 14 (1,2-migration of chlorine) typifying the chemistry in question.…”

Section: Introductionmentioning

confidence: 99%

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Intramolecular Homolytic Translocation Chemistry: An ab Initio Study of 1,n-Halogen Atom Transfer Reactions in Some ω-Haloalkyl Radicals

Schiesser

Wild

1998

J. Org. Chem.

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Ab initio calculations using all-electron (3-21G(()()), 6-311G) and pseudopotential (DZP) basis sets, with (MP2, QCISD) and without (UHF) the inclusion of electron correlation, predict that 1,n-halogen transfer reactions in the 5-halo-1-pentyl (6), 6-halo-1-hexyl (7), and 7-halo-1-heptyl radicals (8) proceed via C(s)- and/or C(2)-symmetric transition states (9-11), except for the 5-bromo-1-pentyl (6, X = Br) radical for which a C(s)-symmetric transition state (9) was located only at the UHF/3-21G(()()) level of theory and the 5-iodo-1-pentyl radical (6, X = I) for which no transition state (9) could be located at any level of theory used in this study. Energy barriers for these translocation reactions of between 120.0 (1,7-iodine transfer) and 191.0 kJ mol(-)(1) (1,5-chlorine transfer) are predicted at the MP2/DZP level of theory; QCISD/DZP (single-point) calculations predict similar energy barriers. These high energy barriers are a consequence of unfavorable factors associated with ring size and long carbon-halogen separations in transition states (9-11) which lead to significant deviations from the collinear arrangement of attacking and leaving radicals preferred in transition states involved in homolytic substitution reactions at halogen. The dependence of transition state energy on attack angle at halogen has been explored for the attack of methyl radical at chloromethane. At the MP2/DZP level of theory, attack angles of between 80 and 90 degrees are calculated to lead to increases in energy barrier of about 100 kJ mol(-)(1) when compared with the collinear (180 degrees ) arrangement of attacking and leaving groups. The mechanistic implications of these predictions are discussed.

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Section: 6-translocations In 6-halo-1-hexyl Radicalssupporting

confidence: 76%

Section: 6-translocations In 6-halo-1-hexyl Radicalsmentioning

confidence: 91%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Intramolecular Homolytic Translocation Chemistry: An ab Initio Study of 1,n-Halogen Atom Transfer Reactions in Some ω-Haloalkyl Radicals

Schiesser

Wild

1998

J. Org. Chem.

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“…Pitt and Fowler reported a radical catalyzed rearrangement in trisilanethiols (e.g. 5), 7 while similar shifts in trialkylsilyl and germyl aminoxyls (6) have also been observed. 8-10 Interestingly, we are only aware of one example in which a chalcogen-containing group undergoes intramolecular homolytic translocation, 11 and no examples involving halogen.…”

Section: Introductionmentioning

confidence: 74%

“…It is generally agreed that homolytic substitution by a radical (R ؒ ) at a group (Y) proceeds either via a transition state (7) in which the attacking and leaving groups adopt a colinear (or nearly so) arrangement resulting in Walden inversion, or with the involvement of a hypervalent intermediate (8) which may or may not undergo pseudorotation prior to dissociation. 1 The (1,n) translocation of the trialkylsilyl group from carbon to oxygen typifies the intramolecular version of this reaction which might be expected to proceed via either transition state (9) or intermediate (10).…”

Section: Introductionmentioning

confidence: 99%