The Stille Reaction

The Stille Reaction - catalyst RX Pd(II BrSnBu 3 PhSnBu 3...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: catalyst RX Pd(II) BrSnBu 3 PhSnBu 3 PhSnBu 3 Bu 3 SnBr MX RI Pd(II)L 2 X H Pd(PPh 3 ) 4 Pd(OAc) 2 Pd R L I L O Pd L L I R Chem 215 Myers Reviews: Farina, V.; Krishnamurthy, V.; Scott, W. J. Org. React. 1998 , 50 , 1652. Stille, J. K. Angew. Chem., Int. Ed. Engl. 1986 , 25 , 508524. Mitchell, T. N. In Metal-catalyzed Cross-coupling Reactions , Diederich, F., and Stang, P. J., Eds.; Generalized Cross-Coupling: R'M R and R' are sp 2 hybridized Wiley-VCH: New York, 1998 , pp. 167202. RR' X = I, OSO 2 CF 3 , Br, Cl M = Sn, B, Zr, Zn catalyst = Pd (sometimes Ni) Mechanism: Pd(0)L n p-TolBr oxidative addition reductive elimination transmetalation p- TolPd(II)L m Br p- TolPd(II)L m Ph p-TolPh Farina, V.; Krishnamurthy, V.; Scott, W. J. The Stille Reaction ; John Wiley & Sons: New York, 1998 . A specific example: Transmetalation is proposed to be the rate determining step with most substrates. -hydride elimination can be a serious side reaction within alkyl palladium intermediates. Oxidative addition and reductive elimination steps occur with retention of configuration for sp 2-hybridized substrates. Many functional groups are tolerated (e.g., CO 2 R, CN, OH, CHO). Relative order of ligand transfer from Sn: alkynyl > alkenyl > aryl > allyl = benzyl > -alkoxyalkyl > alkyl The details of the mechanism are still being elucidated, and the mechanism may change with Casado, A. L.; Espinet, P. J. Am. Chem. Soc. 1998 , 120 , 89788985. Stille Reaction conditions: Catalyst: Commercially available Pd(II) or Pd(0) sources. Examples: Pd 2 (dba) 3 Typically: p-TolBr + Pd catalyst p-TolPh + Oxidative addition initally gives a cis complex that rapidly isomerizes to its trans isomer: PdL 2 cis trans fast HPd(II)L 2 X + different reaction conditions: dba = Casado, A. L.; Espinet, P. Organometallics 1998 , 17 , 954959. Andrew Haidle Intramolecular: Duncton, M. A. J.; Pattenden, G. J. Chem. Soc., Perkin Trans. 1 1999 , 12351246. Solid phase: Franzn, R. Can. J. Chem. 2000 , 78 , 957962. The Stille Reaction I S n B u 3 F a r i n a , V . ; K a p a d i a , S . ; K r i s h n a n , B . ; W a n g , C . ; L i e b e s k i n d , L . S . J . O r g . C h e m . 1 9 9 4 , 5 9 , 5 9 5 5 9 1 1 . A d d i t i v e s : C u I c a n i n c r e a s e t h e r e a c t i o n r a t e b y > 1 2 . r e l a t i v e r a t e 1 1 1 1 4 P d 2 ( d b a ) 3 ( 5 m o l % ) P P h 3 ( 2 m o l % ) d i o x a n e , 5 C m o l % C u I T h e r a t e i n c r e a s e i s a t t r i b u t e d t o t h e f r e e l i g a n d s c a v e n g i n g a b i l i t y o f C u I ; s t r o n g l i g a n d s i n s o l u t i o n a r e k n o w n t o i n h i b i t t h e r a t e- l i m i t i n g t r a n s m e t a l a t i o n s t e p ....
View Full Document

This note was uploaded on 04/07/2008 for the course CHEM 215 taught by Professor Shair during the Fall '07 term at Harvard.

Page1 / 11

The Stille Reaction - catalyst RX Pd(II BrSnBu 3 PhSnBu 3...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online