Transition state chair versus boat

This section will describe experimental and theoretical studies of the structure of the transition state with a focus on the extent of bond formation and cleavage. A discussion of chair versus boat transition states is left to the section on stereochemistry. 

Dolbier Jr., W. R. Palmer, K. W. Effect of terminal flnorine substitution on the Cope rearrangement boat versus chair transition state. Evidence for a very significant fluorine steric effect, J. Am. Chem. Soc. 1993,115,9349-9350. 

The tandem Cope-Cltdsen rearrangement of triene (96 equation 14) creates a product with three new stereogenic centers. Only two of the four possible stereoisomers are formed, namely, aldehydes (100) and (98) in a 78 22 ratio. The factors that control the stereochemistry are the chair-like versus boat-like transition state of the Cope rearrangement (96 giving 97) and the formation of the carbon-carbon bond in... 

Stereochemistry of the Cope Rearrangement Boat versus Chair Transition State... 

In 1983 Ireland and Varney examined the propensity for axial versus equatorial attack in the rearrangement of cyclohexenyl acetates (Scheme 4.40) [42]. They observed a ca. 10 1 preference for axial attack of the sUyl ketene acetal to selectively afford the higher energy 1,4-ds isomer. Although either chair or boat transition states would afford the observed product, the authors argued that the chair transition state is less hindered for the acetate-derived sUyl ketene acetal. They also studied the rearrangements of the propionate-derived E- and Z-sUyl ketene acetals. While the axial attack was still favored, the axial/equatorial ratio decreased to... 

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