Transcript 6. Low valent of Vanadium catalyst in organic synthesis

Low valent of Vanadium
catalyst
in organic synthesis
I. Oxidation of Alcohols
*clean technological process
and no halogenated solvents are involved
Laxmidhar Rout, Adv. Synth. Catal. 2007, 349, 846 – 848
mechanism
II.Pinacol Coupling Reaction
1. Secondary Aliphatic Aldehydes
Toshikazu Hirao, J. Org. Chem. 1998, 63, 2812-281
mechanism
Toshikazu Hirao, Top Curr Chem . 2007, 279: 53–75
2.intramolecular coupling reaction of 1,5diketone
Toshikazu Hirao, J. Org. Chem. 1998, 63, 2812-2813
3.Aromatic aldehydes（solvent：water）
No addition
of a chlorosilane
Xu, and Toshikazu Hirao
J. Org. Chem., 2005, 70 (21), 8594-8596
4. aliphatic aldehydes with
aromatic aldehyde(bearing a chiral auxiliary）
• CAT:[V2Cl3(THF)6]2[Zn2Cl6] (V:II)
• some aliphatic aldehydes + aromatic aldehyde(bearing a chiral auxiliary )
→1,2- diols
• diastereoisomeric ratios up to 91:9 and enantiomeric excesses up to 84%.
Tetrahedron:Asymmetry, 1990, 1(6), 355-358
III. Homocoupling
1. Coupling of Aldehydes
The yield of 2a depended on the amount of chlorotrimethylsilane
Toshikazu Hirao, J. Org. Chem. 1996, 61, 366-367
2.Coupling of Aldimines
Bunpei Hatano, Akiya Ogawa, and Toshikazu Hirao*
J. Org. Chem., 1998, 25, 9423.
mechanism
IV. Related Radical-Like Coupling
Toshikazu Hirao, J. Org. Chem. 1998, 63, 2812-2813
[V2Cl3(THF)6]2,[Zn2Cl6],(V:II),freshly prepared
from VCl3(THF)3 (V:III)by the reduction with Zn
Tsutomu Inokuchi, J. Org. Chem., 1991, 16, 4983-4985
mechanism
b:*Carried out in CH2Cl2-THF.
Tsutomu Inokuchi, J. Org. Chem., 1991, 16, 4983-4985
Cyclization of Olefinic Iodoethers
to Tetrahydrofurans
Cp2TiCl2 was found to be superior to Cp2VCl2 as a
catalyst under these reaction conditions
Longhu Zhou, and Toshikazu Hirao
J. Org. Chem., 2003, 68 (4), 1633-1635
V. stereoselective cyclodimerization
Reaction conditions:
benzylidene malononitrile (1 mmol),
Cp2VCl2 (5 mol%), Zn (2 mmol), Me3SiCl (2 mmol),
DMF (5 mL), Ar, rt, 3 h.
Longhu Zhou and Toshikazu Hirao,
Tetrahedron Letters, 2000, 41, 8517–8521
3a (24% yield with excellent diastereoselectivity (98:2)
2a (58% yield, 80:20)
*3a was converted to 2a on treatment with silica gel overnight
*18 h, only 2a was formed,
VI. Dehalogenative Coupling
*R2 is bigger.
*the coordination of the phosphorus raises the reduction capability
and selectivity.
*the bulky reductant is liable to approach the bromide from the
less hindered side
Toshikazu Hirao，J. Org. Chem., 1993, 58 (23), 6529-6530
VII. A Novel C−C Single Bond
Formation
1. V with Grinard reagent *cleavage of the C-O bond at the benzylic
position was easy
Yasutaka Kataoka,*J. Org. Chem. 1996, 61, 6094-6095
* clarify the effect
of the added O2
As the amount of allyl bromide increased, the yield of the coupling
product 1a decreased gradually while the amount of 3 increased.
Mechanism:
1a, under high dilution conditions.
Yasutaka Kataoka,*J. Org. Chem. 1997, 62, 8109-8113
The cleavage of the C-O bond at the allylic position also proceeded similarly.
2. V with ZnR2
the alkylation of carbonyl compounds
the pinacolcoupling reaction
the deoxygenative coupling
reaction of carbonyl compounds
Yasutaka Kataoka, J. Org. Chem. 1996, 61, 6094-6095
• a competitive reaction between an aldehyde and a ketone
Yasutaka Kataoka, Isamu Makihira, Masaru Utsunomiya,
J. Org. Chem., 1997, 62 (24), 8540-8543
3. V with Zn and allylic bromide
*direct construction of asymmetric quaternary carbons
Tetrahedron Letters, 1995, 36, 6495-6498
mechanism
vanadium(II) species prepared in situ from VCl3(thf)3 and Zn
VIII .cross-coupling reaction
1.Alkyl Halides with Aryl Griganard Reagents
Br
+
ArMgBr
Ar
cat.VCl3
THF,25oC,1 h
VCl3(0.05mmol)
Br
+
PhMgBr
(1.0mmol)
THF,reflux,1 h
Ph
(50%)
Mechanism：
Br
Ph
Shigeo Yasuda,Hideki Yorimitsu*
Bull.Chem.Soc. Jpn. 2008, 81, 287-290
Br
VCl3(0.05mmol)
PhMgBr(1.0mmol)
THF,25oC,1 h,75%
Ph
0.50mmol
VCl3(0.05mmol)
PhMgBr(1.0mmol)
Br
THF,25oC,1 h,45%
0.50mmol (16% recovery of the starting meterial)
Prove the radical intermediate
mechanism
VCl3
4ArMgBr
R-X
ArMgBr
-
[Ar4VMgBr]
[R-X]
MgBr+
-
[Ar4V]
[Ar3V]
X
R
R-Ar
[RAr4V]
IX. Potent Dinuclear Catalysts
for Olefin Copolymerization