CYCLOHEXENE-3,3,6,6-d4 A USEFUL COMPOUND FOR THE STUDY OF MECHANISM AND STRUCTURE

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Abstract
The title compound (I) was prepared by Diels–Alder reaction of butadiene-1,1,4,4-d4 with ethylene. The considerations which led to the synthesis of I are presented and some examples are then given of how use of I can simplify the study of, and provide new information about, a number of different kinds of problems. In the proton magnetic resonance (n.m.r.) spectra of the products of additions to I, the tertiary protons usually appear as clearly defined quartets. Since |JAB| can be read directly from these spectra, both the stereochemistry of the additions and the conformations of the products can be deduced. Thus, oxymercuration of I is clearly a trans addition and Na/Hg reduction of the mercury takes place with retention of configuration. When the second step is performed in D2O, the oxymercuration–reduction sequence represents a convenient route for the trans addition of DOH to a double bond. Deuteroboration provided an example of cis addition of DOH to I. Acid-catalyzed hydration of I resulted in scrambling of the deuterium atoms. The value of GBr/OH is small; GBr/OHis 600 cal/mol. The position of the double bond in a product resulting from allylic substitution of I is determined by integration of the n.m.r. spectrum. Relative to I, the possibilities are no rearrangement, 50% rearrangement, and 100% rearrangement of the double bond. The first product of allylic substitution by N-bromosuccinimide shows no rearrangement; therefore, this reaction does not require a "free" radical intermediate. The structure of an adduct formed during allylic acetoxylation of I by mercuric acetate (the Treibs reaction) has been determined.

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