Nucleophilic substitution at the bridgehead of 1,4-dihalobicyclo[2.2.2]octanes : An abnormal leaving group mobility order

✍ Scribed by William Adcock; V.Sankar Iyer; Gaik B. Kok; William Kitching

• Book ID: 104226374
• Publisher: Elsevier Science
• Year: 1983
• Tongue: French
• Weight: 151 KB
• Volume: 24
• Category: Article
• ISSN: 0040-4039
• DOI: 10.1016/s0040-4039(00)94233-3

✦ Synopsis

Stannylation of 1-bromo-and 1-chloro-4-iodobicyclo[2.2.2]octane with (trimethyltin) lithium indicate an abnormal leaving group mobility (Br>I>Cl). In the course of an investigation of polar substituent effects in the bicyclo[2.2.2]octane (BCO)ring system we had occasion to synthesize a series of 4-substituted bicyclo[2.2.2]octyl-1-trimethylstannanes (l).l These compounds were prepared by treating the appropriate 4-substituted bicyclo[2.2.2]oct-l-y1 iodides (2) with (trimethyltin)lithium (MesSnLi) in tetrahydrofuran at 0°C in the standard way.2 Although a full description of these syntheses will be presented in a full paper in the near future, completely unexpected aspects of two of the preparations (X=Cl and Br) prompt this report which extends the mechanistic picture for such substitution (stannylation) processes 3-6 by arguing the possibility that the elusive [2.2.2]propellane (3) (tricyclo[2.2.2.01'4]octane)7 is functioning as a transient intermediate in these cases.