Stereochemistry and mechanisms of the addition of deuterium chloride to bicyclo[2.2.1]heptadiene (norbornadiene) and to tetracyclo[3.2.02,7.04,6]heptane (quadricyclene)
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Addition of hydrogen chloride and deuterium chloride to bicyclo [2.2.1] heptadiene (I, norbornadiene) results in (unlabeled and labeled, respectively) exo-dehydronorbornyl chloride (III) and nortricyclyl chloride (IV). The ratio of III/IV varies from ,75-85%/25-15% depending upon the solvent and addendum. Labeled III is composed of 57% (+/- 1 %) exo-cis-3-deuterio-2-dehydronorbornyl chloride (IIIa) and 43% syn-7-deuterio-2exo-dehydronorbornyl chloride (IIIb). Addition of deuterium chloride and hydrogen chloride to tetracyclo-[184.108.40.206^2,7.0^4-,6]heptane (II, quadricyclene) gave (respectively, labeled and unlabeled) III and IV in ratios of 80-87% III/20-13% IV. Labeled III (from II) was composed of 58% (+/- l%) IIIa and 42% IIIb. The mechanism(s) of addition to I and II must be very similar and neither addition can involve a symmetrically bridged cation as the sole precursor to III. Ionic cleavage of the cyclopropane rings of II are by the inversion process only.