GAS-PHASE REACTIVITY OF AROMATIC SILANES - THE REACTION OF PH(CH2)(X)SIME3 (X=0 OR 1) WITH CATIONIC ELECTROPHILES

The reactivity of BTS (x = 1) and PTS (x = 0) towards charged electrop hiles has been studied in the gas phase with the aim of assessing the activating and directive properties of the Me,Si(CH,), group in a solv ent-free environment. BTS is confirmed to be highly activated towards electrophilic attack, which is directed to the ortho/para positions, c onsistent with a PA value of 200 +/- 1 kcal mol(-1). Ipso attack follo wed by desilylation is a dominant pathway in the reactions of PTS, ten ding to obscure its intrinsic reactivity. However, the reaction of a m ild methylating agent, Me(2)Cl(+), yields a meaningful reactivity scar e: BTS > p-xylene > PTS > toluene.