Rhodium-catalyzed transformation of propargyl alcohol derivatives to 2-silylmethyl-2-alkenals
摘要:
Propargyl-type alcohols (6) and the corresponding esters of carbonic acid (4) or acetic acid (5) react with two equivalents of Me2PhSiH in the presence of catalytic amounts of Rh-4(CO)(12) under CO pressure at 100 degrees C to give 2-(dimethylphenylsiIylmethyl)-2-alkenals (3), whereas 2-substituted-3-(dimethylphenylsilyl)propenals (7, 8 and 9) are also isolated with the concomitant formation of 3 when a similar reaction is operated with shortage of Me2PhSiH or with lowering of reaction temperature. The isolated 9 is selectively converted to 3 by the Rh-4(CO)(12) catalyzed reaction with Me2PhSiH under CO pressure. This fact suggests that the transformation of 4, 5 or 6 to 3 is accomplished by either a one-pot procedure or a stepwise procedure relayed by 7, 8 or 9. Usefulness of this protocol is demonstrated by the synthesis of 18 in which ethisterone (17) is directly converted by a one-pot procedure. (C) 1999 Elsevier Science S.A. All rights reserved.
Propargyl-type alcohols (6) and the corresponding esters of carbonic acid (4) or acetic acid (5) react with two equivalents of Me2PhSiH in the presence of catalytic amounts of Rh-4(CO)(12) under CO pressure at 100 degrees C to give 2-(dimethylphenylsiIylmethyl)-2-alkenals (3), whereas 2-substituted-3-(dimethylphenylsilyl)propenals (7, 8 and 9) are also isolated with the concomitant formation of 3 when a similar reaction is operated with shortage of Me2PhSiH or with lowering of reaction temperature. The isolated 9 is selectively converted to 3 by the Rh-4(CO)(12) catalyzed reaction with Me2PhSiH under CO pressure. This fact suggests that the transformation of 4, 5 or 6 to 3 is accomplished by either a one-pot procedure or a stepwise procedure relayed by 7, 8 or 9. Usefulness of this protocol is demonstrated by the synthesis of 18 in which ethisterone (17) is directly converted by a one-pot procedure. (C) 1999 Elsevier Science S.A. All rights reserved.