Article

Bond rotation dynamics of N-cycloalkenyl-N-benzyl alpha-haloacetamide derivatives.

Department of Chemistry, University of Pittsburgh, Pittsburgh Pennsylvania 15260, USA.
The Journal of Organic Chemistry (impact factor: 4.45). 06/2009; 74(11):4262-6. DOI:10.1021/jo900491w pp.4262-6
Source: PubMed

ABSTRACT Barriers to rotation of the N-alkenyl bond in a series of N-cycloalkenyl-N-benzyl alpha-haloacetamide derivatives have been measured by variable-temperature NMR experiments. The barriers range from 10 to 18 kcal/mol, depending on ring size and on substituents on the cycloalkene and the amide. The observed trends aid in the design of substituent combinations that provide resolvable enantiomers or diastereomers at ambient temperature. The compounds undergo 4-exo and 5-endo radical cyclizations at rates that may be faster or slower than the estimated rate of N-alkenyl bond rotation in the derived radicals, depending on the substituents.

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Keywords

4-exo
 
ambient temperature
 
amide
 
Barriers
 
barriers range
 
cycloalkene
 
derived radicals
 
diastereomers
 
N-alkenyl bond
 
N-alkenyl bond rotation
 
N-cycloalkenyl-N-benzyl alpha-haloacetamide derivatives
 
observed trends aid
 
provide resolvable enantiomers
 
slower
 
substituents
 
variable-temperature NMR experiments