GENERATION OF SILYLETHYNOLATES FROM DISILYLKETENES Nu O - - PowerPoint PPT Presentation

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GENERATION OF SILYLETHYNOLATES FROM DISILYLKETENES Nu O transmetallation addition O O Si SiNu Si Si Nu Si Si CO Si C yield, % O t -BuMe 2 SiOTf Nu Me 3 Si A B Nu THF SiMe 3 HMPA PhLi 39 51

SLIDE 1

CO– SiC Si

Si

GENERATION OF SILYLETHYNOLATES FROM DISILYLKETENES

Si – Nu– transmetallation addition Si Si O– Nu – SiNu Me3Si

SiMe3 Nu THF HMPA t-BuMe2Si

SiMe3 + Me3Si SiMe3 OSiMe2t-Bu R t-BuMe2SiOTf Nu yield, % 39 PhLi MeLi t-BuLi t-BuOK 51 32 53 47 84 A B A B

SLIDE 2

Pd–MEDIATED KETENYLATION USING SILYLETHYNOLATE

Si(i-Pr)3 trace

Si(i-Pr)3 0% [(η3-C3H5)PdCl]2 Cl –30 ˚C –30 ˚C Me3Si

Si(i-Pr)3 KOt-Bu THF HMPA (i-Pr)3SiC COK K

Si(i-Pr)3 THF

SLIDE 3

Si Pd COK SiC – KCl –Pd(0)Ln COSi SiC Si

Si Y Pd(0)Ln Pd Ln Y – SiY Cl 2 +

Pd YNOLATE INTERMEDIATE

PdLn(OC≡CSi)

SLIDE 4

Pd–CATALYZED ALLYLATION OF DISILYLKETENES

Y +

Si(i-Pr)3 Y OCO2CH3 OAc 77 75 yield, % THF rt, 12 h Me3Si

Si(i-Pr)3 Pd(PPh3)4 Cl Pd Si

Si OR Si OR Pd(OC CSi) ketene:allyl compound:Pd = 20:20:1

SLIDE 5

OAc +

R2 THF rt, 12 h yield, % R1

R2 Pd(PPh3)4 R2

REACTION OF VARIOUS SILYLKETENES

ketene:allyl acetate:Pd = 20:20:1 SiMe2t-Bu 56 R1 SiMe3 SiMe3 Si(i-Pr)3 75 SiMe3 SiMe3 60 SiMe3 SiMe3 63a SiMe3

a Ketene:allyl acetate:Pd = 20:40:1.

n-Bu

SLIDE 6

VARIOUS ALLYL ACETATES

+ 67 31a THF rt, 5–12 h Me3Si

Si(i-Pr)3 Pd(PPh3)4 42 alyll acetate 57 H

Si(i-Pr)3 R

Si(i-Pr)3 yield, % ketene:allyl acetate:Pd = 5:5:1 (R = H, Me) OAc R3 R4 R1 R4 R3 R1 R1 R2 R3 H H Me Me H H

a Side reaction products

H H H R2 R2 R4 H H Ph Ph H H H 0a Me Me H H R1 R2 R3 H H Me Me H H Ph H H R4 H H H Ph H H H Me Me H H product

SLIDE 7

A POSSIBLE CATALYTIC CYCLE

PdLn Y Pd SiY Si

Si

Si Ln Y PdLn(OC≡CSi)

SLIDE 8

ALLYLIC SUBSTITUTION WITH ORGANOSILICON COMPOUNDS

Y R1 R3Si–Nu R3Si–Y Nu R1 + + Pd Nu

J. Tsuji et al., Chem. Lett.,1983, 1325.

R1 R2 O R1O R2 O SiR3 CN Y

J. Tsuji et al., Tetrahedron Lett., 1984, 25, 4783.
Y. Tsuji et al., J. Org. Chem., 1996, 61, 5779.
Y. Tsuji et al., Organometallics., 1998, 17, 4835.

OCO2CH3 OAc OCOCF3 : :

SLIDE 9

A PRECEDENT FOR C–C BOND FORMATION USING SILYLETHYNOLATE

AlMe3 H+ O COLi Me3SiC O SiMe3 O

S. Murai et al., J. Am. Chem. Soc., 1996, 118, 7634.

–78 → 20 ˚C 93% Li N2 Me3Si –78 ˚C –78 → 0 ˚C CO + 1 atm

SLIDE 10