Zirconocene chloride hydride

A further improvement in the cuprate-based methodology for producing PGs utilizes a one-pot procedure (203). The CO-chain precursor (67) was first functionalized with zirconocene chloride hydride ia THF. The vinyl zirconium iatermediate was transmetalated direcdy by treatment with two equivalents of / -butyUithium or methyUithium at —30 to —70° C. Sequential addition of copper cyanide and methyUithium eUcited the /V situ generation of the higher order cyanocuprate which was then reacted with the protected enone to give the PG. 

Acylzirconocene chloride derivatives are easily accessible in a one-pot procedure through the hydrozirconation of alkene or alkyne derivatives with zirconocene chloride hydride (Schwartz reagent) [Cp2Zr(H)Cl, Cp = cyclopentadienyl] and subsequent insertion of carbon monoxide (CO) into the alkyl— or alkenyl—zirconium bond under atmospheric pressure (Scheme 5.1) [2],... 

Many examples exist for Pd-catalyzed cross-couplings of alkenylzirconocenes with simple carbocyclic aryl or alkenyl halides, whereas few precedents are seen for the coupling of alkenylzirconocenes with heteroaryl halides. Undheim and coworkers reported a Pd-catalyzed cross-coupling of 2,4-dichloropyrimidine with alkenylzirconocene [50]. Hydrozirconation of hexyne readily took place at room temperature with zirconocene chloride hydride in benzene. The resulting hexenylzirconocene chloride (76) was then coupled with 2,4-dichloropyrimidine at the more electrophilic 4 position, giving rise to 2-chloro-4-[( )-l-hexenyl]pyrimidine (77). 

A sample of Taxol (14.7 g, 17 mmol) was dissolved in pyridine (150 mL) and chlorotriethylsilane (23.03 g, 147 mmol) was added. The reaction was stirred at 25°C under N2. After 20 hours the reaction appeared complete by TLC analysis (7% MeOH/CH2CI2). The mixture was concentrated to remove the pyridine. The residue was dissolved in CH2CI2 and washed with water, 10% CuS04, NaHC03 and brine successively. The organic layer was dried over MgS04, and concentrated to yield 20.89 g of the crude 2,7 -bis(triethylsilyl) Taxol. A portion of crude 2, 7-bis(triethylsilyl) Taxol (14.50 g, 13.4 mmol) was dissolved in dry THF (150 mL). Zirconocene chloride hydride (7.75 g, 30.2 mmol) was added. The reaction was stirred at 25°C under l l2. After 20 hours the reaction appeared complete by TLC analysis. The mixture was poured into... 

Zirconocene hydrochloride aldrich Zirconocene chloride hydride Zirconium, chlorodi-ji-cyclopentadienylhydro- (8) Zirconium, chlorobis(r 5-2,4-cyclopentadien-1-yl)hydro- (9) (37342-97-5)... 

Hydrocarboxylation can also be used in the synthesis of heterocycles if the heterofunction is introduced at an appropriate position within the substrate. Thus, preparation of 2,4-disub-stituted 2-buten-4-olides can be achieved via stoichiometric transformation of a protected optically active propargyl alcohol without loss of optical activity30. Sequential treatment with zirconocene chloride hydride (Schwartz s reagent), carbon monoxide, and iodine gives a 55% yield of (S)-2-ethyl-4-isobutyl-2-buten-4-olide30. This reaction resembles the intramolecular hydrocarboxylation of allylic alcohols. 

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