Synthetic Applications of Intramolecular Insertion in Arylcarbenes. IV. o-Alkoxy-, Dialkylamino- and Alkylthio-1-phenylethylidenes

1979 ◽  
Vol 32 (1) ◽  
pp. 123 ◽  
Author(s):  
WD Crow ◽  
H McNab
Keyword(s):  
Transition State ◽  
Gas Phase ◽  
Side Chains ◽  
Ortho Position ◽  
No Formation ◽  
Carbene Insertion ◽  
Transition State Geometry

A series of 1-phenylethylidenes, substituted in the ortho-position by alkoxy, dialkylamino and alkylthio side chains containing up to three carbon atoms, has been generated in the gas phase and pyrolysed at 250-750�/0.05-0.30 mm. Carbene insertion to form five-membered heterocyclic rings predominates, with up to 20% Bamford-Stevens insertion, to give the styrenes; little or no formation of six-membered rings is observed. In cases where stereoselective insertion is possible, the trans-disubstituted heterocycle is formed preferentially, the selectivity being greatest in the case of dialkylamino substitution. The mechanisms involved are discussed in terms of transition state geometry.

Synthetic Applications of Intramolecular Insertion in Arylcarbenes. II. o-Alkoxy-, Dialkylamino- and Alkylthio-phenylcarbenes

1979 ◽  
Vol 32 (1) ◽  
pp. 99 ◽  
Author(s):  
WD Crow ◽  
H McNab
Keyword(s):  
Transition State ◽  
Gas Phase ◽  
Membered Ring ◽  
Ring Formation ◽  
High Yield ◽  
Side Chains ◽  
Ortho Position ◽  
Carbene Insertion ◽  
Donor Capacity

A series of phenylcarbenes, substituted in the ortho-position by alkoxy, dialkylamino and alkylthio side chains containing up to three carbon atoms, has been generated in the gas phase and pyrolysed at 250-750�/0.05-0.20mm. Carbene insertion occurs in moderate to high yield to give the appropriate five-and six-membered heterocyclics, the former predominating. The regioselectivity of the carbene insertion (five-membered ring us six-membered ring) is highest in the case of the alkoxy and dialkylamino compounds, where six-membered-ring formation is relatively minor; in the case of the alkylthiophenylcarbenes, the selectivity in favour of the smaller ring is, by comparison, small. The reasons for this are discussed in terms of the geometry of the transition state and the donor capacity of the heteroatom.

scholarly journals Advances in Automated Transition State Theory Calculations: Improvements on the AutoTST Framework

2020 ◽  
Author(s):  
Nathan Harms ◽  
Carl Underkoffler ◽  
Richard West
Keyword(s):  
Transition State ◽  
Kinetic Parameters ◽  
Transition State Theory ◽  
Vibrational Analysis ◽  
Chemical Kinetic ◽  
State Theory ◽  
Combustion Chemistry ◽  
Transition State Geometry ◽  
Substantial Progress ◽  
Symmetry Number

<div>Kinetic modeling of combustion chemistry has made substantial progress in recent years with the development of increasingly detailed models. However, many of the chemical kinetic parameters utilized in detailed models are estimated, often inaccurately. To help replace rate estimates with more accurate calculations, we have developed AutoTST, an automated Transition State Theory rate calculator. This work describes improvements to AutoTST, including: a systematic conformer search to find an ensemble of low energy conformers, vibrational analysis to validate transition state geometries, more accurate symmetry number calculations, and a hindered rotor treatment when deriving kinetics. These improvements resulted in location of transition state geometry for 93% of cases and generation of kinetic parameters for 74% of cases. Newly calculated parameters agree well with benchmark calculations and perform well when used to replace estimated parameters in a detailed kinetic model of methanol combustion.</div>

Synthetic applications of intramolecular insertion in arylcarbenes. VII. Aryl-substituted benzocycloalkenylidenes

1984 ◽  
Vol 37 (9) ◽  
pp. 1915 ◽  
Author(s):  
WD Crow ◽  
U Engkaninan-Low ◽  
YT Pang
Keyword(s):  
Gas Phase ◽  
Phenyl Ring ◽  
Side Chain ◽  
Electronic Effects ◽  
Carbene Insertion

A series of benzo-fused cyclic carbenes, bearing suitably located alkoxy substituents in the phenyl ring, has been generated in the gas phase and pyrolysed at 250�/0.002-0.40 mm. In all cases, carbene insertion into the adjacent C-H bond (Bamford-Stevens insertion) occurs, either exclusively or predominantly, with up to 35% 1,5 C-H insertion in the alkoxy side chain to form peri-fused tricyclic heterocycles. These results are rationalized in terms of geometrical and electronic effects.

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