low valent of vanadium catalyst in organic synthesis

Low valent of Vanadium catalyst

in organic synthesis

I. Oxidation of Alcohols

Laxmidhar Rout, Adv. Synth. Catal. 2007, 349, 846 – 848

*clean technological process and no halogenated solvents are involved

mechanism

II.Pinacol Coupling Reaction1. Secondary Aliphatic Aldehydes

Toshikazu Hirao, J. Org. Chem. 1998, 63, 2812-2813

mechanism

Toshikazu Hirao, Top Curr Chem . 2007, 279: 53–75

2.intramolecular coupling reaction of 1,5-diketone

Toshikazu Hirao, J. Org. Chem. 1998, 63, 2812-2813

3.Aromatic aldehydes（ solvent： water）

Xu, and Toshikazu HiraoJ. Org. Chem., 2005, 70 (21), 8594-8596

No additionof a chlorosilane

• 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

4. aliphatic aldehydes with aromatic aldehyde(bearing a chiral auxiliary）

III. Homocoupling

Toshikazu Hirao, J. Org. Chem. 1996, 61, 366-367

The yield of 2a depended on the amount of chlorotrimethylsilane

1. Coupling of Aldehydes

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 preparedfrom 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 acatalyst under these reaction conditions

Longhu Zhou, and Toshikazu HiraoJ. Org. Chem., 2003, 68 (4), 1633-1635

V. stereoselective cyclodimerization

Longhu Zhou and Toshikazu Hirao,Tetrahedron Letters, 2000, 41, 8517–8521

Reaction conditions: benzylidene malononitrile (1 mmol), Cp2VCl2 (5 mol%), Zn (2 mmol), Me3SiCl (2 mmol), DMF (5 mL), Ar, rt, 3 h.

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

Yasutaka Kataoka,*J. Org. Chem. 1996, 61, 6094-6095

1. V with Grinard reagent *cleavage of the C-O bond at the benzylic position was easy

As the amount of allyl bromide increased, the yield of the coupling product 1a decreased gradually while the amount of 3 increased.

* clarify the effect of the added O2

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.

Yasutaka Kataoka, J. Org. Chem. 1996, 61, 6094-6095

2. V with ZnR2

the alkylation of carbonyl compounds

the pinacolcoupling reaction

the deoxygenative couplingreaction of carbonyl compounds

Yasutaka Kataoka, Isamu Makihira, Masaru Utsunomiya, J. Org. Chem., 1997, 62 (24), 8540-8543

• a competitive reaction between an aldehyde and a ketone

*direct construction of asymmetric quaternary carbons

Tetrahedron Letters, 1995, 36, 6495-6498

3. V with Zn and allylic bromide

mechanism

vanadium(II) species prepared in situ from VCl3(thf)3 and Zn

VIII .cross-coupling reaction

Br+ ArMgBr

Arcat.VCl3

THF,25oC,1 h

1.Alkyl Halides with Aryl Griganard Reagents

Shigeo Yasuda,Hideki Yorimitsu*Bull.Chem.Soc. Jpn. 2008, 81, 287-290

Br+ PhMgBr

(1.0mmol)

VCl3(0.05mmol)

THF,reflux,1 h Ph

Br

(50%)

Ph

Mechanism：

Br

0.50mmol

0.50mmol

Ph

VCl3(0.05mmol)PhMgBr(1.0mmol)

THF,25oC,1 h,75%

VCl3(0.05mmol)PhMgBr(1.0mmol)

THF,25oC,1 h,45%

(16% recovery of the starting meterial)

Br

Prove the radical intermediate

mechanismVCl3

4ArMgBr

[Ar4VMgBr]

MgBr+

R-X

[R-X]-

[Ar4V]X-

[RAr4V]

[Ar3V]

R-Ar

ArMgBr

R

IX. Potent Dinuclear Catalysts for Olefin Copolymerization