Acid-Catalyzed Protium-Deuterium Exchange in Norbornyl and Aromatic Systems

Abstract

<p>Solvolysis of nortricyclyl bromide (9a), nortricyclyl chloride (9b), nortricyclanol (9c), S- and 7-norbornenols (10b, 15), syn-7-hydroxy-exo-2-norborneol ([8a, and exo-2,3-cpoxynorbornane (19) in a sealed tube at 250º in 10% v/v Ol₃COOD-D₂O or D₂O alone in the case of the halonortricyclanes yields multiple but incomplete deuteration of the products 2-(cyclopentene)- acetaldehyde (11), 3-(cyclopentene) acetaldehyde (12), 3-(cyclohexene)carbox-aldehyde (13) and norcaphor (14). Similar results are obtained with norbornadiene (21).</p> <p>Treatment of norbornene (53), nortricyclane (54), norbornyl acetate (55) and exo-norborneol (56) with 10% v/v CH₃COOD-D₂O at 250º yields primarily completely deuterated 2-norborneol in-reasonable yields. In contrast, treatment of benzonorbornadiene (64) under identical conditions results in selective deuteration of the aromatic ring of the product, benzonorborneol (65, 66).</p> <p>Treatment of phenol (76), benzene (84), biphenyl (85), σ- and m- xylene (86, 87), benzoic acid (101) and pyridine (102) with 4% v/v conc. HC1 (conc. DCl) in D₂O or D₂O alone in the case of aniline hydrochloride (70) at temperatures between 200-275ºC results in selective deuteration of the aromatic nucleus with excellent isotopic incorporation and quantitative yields in most cases.</p> <p>The high temperature-dilute acid (HTDA) exchange procedure described in the thesis is much superior to presently reported acid-catalyzed deuterium exchange techniques. The method presents substantial advantages, as compared with all other deuterium labelling procedures because of cost, simplicity of procedure, selectivity, freedom from steric effects and side reactions, high degree of isotope incorporation, essentially quantitative yields and most importantly, adaptability to large scale preparations. This process constitutes a new rapid one-step method of not only labelling organic compounds with deuterium and/or tritium but also provides a route for the preparation of ¹⁸O labelled phenols.</p>