Base-catalyzed protium–deuterium exchange in bicyclo[2.2.1]heptanones

Abstract

The rates of NaOD-catalyzed protium–deuterium exo exchange in fenchan-2,5-dione (2) and 1-methyl-5-oxo-camphene (3) are 200 and 7, respectively, relative to epiisofenchone (1). The endo exchange rates in 2 and 3 are 1840 and 4, respectively, relative to 1. These data give information about the relative importances of conjugative, conformational, inductive, strain, and steric effects which may arise when a carbonyl group or a double bond is situated 1,3 to an enolizable center in the 2.2.1 system.

On the Mechanism of Base-catalyzed Hydrogen Isotope Exchange in Cyclic Ketones

“…Kinetic measurements have shown that in dioxane-D20 kHe:f/ k!, ' , : is approximately 650 (2, 3).2 As a part of our studies on the isotope exchange of bicyclic mono-and diketones (3), we have measured the dedeuteration of norcamphor-3,3-d2 (6) in protic media, and have found kDe;;/ k:, ' , H to be 72. 3 In this communication we present our findings and show that the difference between H + D and D + H exchange rates provides information on the mechanism of exchange.…”

“…Stereoselectivity in the base-catalyzed deuteration at the 3-position of norcamphor (1) has been noted by several workers (1)(2)(3). Kinetic measurements have shown that in dioxane-D20 kHe:f/ k!, ' , : is approximately 650 (2, 3).2 As a part of our studies on the isotope exchange of bicyclic mono-and diketones (3), we have measured the dedeuteration of norcamphor-3,3-d2 (6) in protic media, and have found kDe;;/ k:, ' , H to be 72.…”

“…Rates of H + D exchange in 1 and D -+ H exchange in 6 were measured in 60% dioxane-H 2 0 (D20) at 30.0 "C by monitoring the decrease in substrate by mass spectrometry (2,3). The observed rate data are listed in Table 1, and second-order rate constants derived from these are collected in Table 2.…”

13C Chemical Shifts of Highly Substituted Bicyclo[2.2.1]heptanes

“…Through our interest in the chemistry of the bicyclic diones 2,5, and 9, and the enones 7 and 11 (11) we have applied 13C.m.r. to determine whether or not the diones and enones, which certainly exist in synchro or contra twist forms (12) are hybridizationally unusual at the bridgeheads with the angle described by the bonds C,-Cl-C, deviating substantially from the normal 109.5".…”

Towards a complete account of the mechanism of hydrogen isotope exchange of diastereotopic protons of carbon acids. II. Acid- and base-catalyzed enolization of bicyclo[2.2.1]heptan-2-ones. Evidence for exchange by inversion

“…A research program was initiated at that time to detail the mechanistic intricacies of hydrogen isotope exchange (enolization) of bicyclic ketones and determine the effect of groups located remote (P or y) from an a enolizable site. A number of papers documenting our work have been published (9)(10)(11)(12)(13)(14)(15)(16). We noted, most importantly, from a study of the stereoselectivity of H -+ D and D -+ H exchange of l a and its 3,3-dideuteriated analog l b , that the k , , , , /k ,.,,, /,, (k,,,,/k , , , , ) ratio decreased from 660 for exchange of l a in deuteriated medium to 72 for exchange of l b in nondeuteriated medium.…”