REACTIONS OF COMPOUNDS OF THE TYPE (ME(3)SI)(2)C(SIME(2)C(6)H(4)Y)(SIME(2)X) WITH TRIFLUOROACETIC-ACID

The iodides (Me(3)Si)(2)C(SiMe(2)C(6)H(4)Y)(SiMe(2)I), with Y = H, p-O Me, and p-Cl, react with trifluoroacetic acid at 35 degrees C to give the bis(trifluoroacetate) (Me(3)Si)(2)C(SiMe(2)O(2)CCF(3))(2), 8. The initial reaction involves solvolysis at the Si-I bond to give HI and ( Me(3)Si)(2)C(SiMe(2)C(6)H(4)Y)(SiMe(2)OCCF(3)), and the HI then cleave s the Si-aryl bond in the latter and in the starting material to give (Me(3)Si)C(SiMe(2)I)(SiMe(2)O(2)CCF(3)) and (Me(3)Si)(2)C(SiMe(2)I)(2) , which then undergo further solvolysis, with anchimeric assistance by gamma-O2CCF3 or gamma-I to leaving of I-. In the case of the correspo nding reaction of the bromide (Me(3)Si)(2)C(SiMe(2)Ph)(SiMe(2)Br) the dibromide is clearly seen as an intermediate. In keeping with the abov e, when Et(3)N is present to neutralize the HI the reaction of (Me(3)S i)(2)C(SiMe(2)C(6)H(4)Cl-p)(SiMe(2)I) gives only the expected 2)Si)(2) C(SiMe(2)C(6)H(4)Cl-p)(SiMe(2)O(2)CCF(3)). The reactions of the compou nds (Me(3)Si)(2)C(SiMe(2)Ph)(SiMe(2)OR), R = Me or H, also give 8, but the initial reaction is cleavage of the Si-Ph bond by CF3CO2H, and it is suggested that this process is assisted by initial protonation of the OR group followed by transfer of the proton to the nearby ipso car bon atom of the phenyl group.