Stereochemistry of 2-methyl- and 2-phenyl-2-adamantyl cations

✍ Scribed by Herrmann, Roland ;Kirmse, Wolfgang

• Publisher: John Wiley and Sons
• Year: 1995
• Tongue: English
• Weight: 369 KB
• Volume: 1995
• Category: Article
• ISSN: 0947-3440
• DOI: 10.1002/jlac.1995199504100

✦ Synopsis

When both diastereomers of [5-D]-2-methyl-2-adamantyl 2-01s (19a, b) were obtained. The stereoselectivity of secon-2,4-dinitrophenolate (18a) and [5-D]-2-phenyl-2-adamantyl dary 2-adamantyl cations, attributed to cr participation, is ef-2,4-&nitrophenolate (18b) were solvolyzed in 40% aqueous fectively suppressed by charge-stabilizing groups a t (2-2. acetone, 1 : 1 mixtures of (E)and (Z)-[5-D]-2-R-adamantan-Solvolyses of 2-adamantyl esters were originally thought to be ideal examples of unassisted ionization[']. The subsequent literature gave increasing evidence for o participati~n[~-~]. Kinetic and spectroscopic work was supplemented by stereochemical data. Thus the solvolysis of (@-[5-D]-2-adamantyl tosylate (1)[*1 in aqueous acetone was found to proceed with 92% retention of configuration (-+ 3)16]. Acid-catalyzed rearrangement of optically active [4-D]protoadamantan-em-4-01 (4) and solvolysis of the analogous endo tosylate in aqueous-organic media afforded [ 1-D]-adamantan-2-01

(5) with 297% eec71. These results point to the intermediacy of a chiral2-adamantyl cation, depicted as the bridged structure 2.