Zirconocene synthesis

Dimethylselenides, bacterial degradation, 12, 610 Dimethylsilyl bridges, in -titanocenes, 4, 619 Dimethylsilylene-bridged -zirconocenes, synthesis, 4, 949 Dimethyl sulfoxide, for water-solubilization, 1, 827 Dinitrogens... 

Zirconocene complexes containing two indenyl or tetrahydroindenyl groups bridged with short links such as —CH2—CH2— or —Si(CH3)— can produce isotactic polymers of higher a-olefins (32). To synthesize syndiotactic PO, bridged zirconocene complexes with rings of two different types are required, one example of which is isopropyl(cyclopentadienyl)(l-fluorenyl)zirconocene. These complexes are used for the synthesis of syndiotactic PB... 

A concise total synthesis of the indole alkaloid dihydrocorynantheol (101) (Scheme 19), that features two RCM steps and a zirconocene-catalyzed carbo-magnesation [68], is a further example of Martin s interest in applying RCM as a key reaction for the construction of alkaloid frameworks [69]. The first RCM step was applied to bis-allyl amide 96. The resulting intermediate 97 was directly subjected to carbomagnesation and subsequent elimination to deliver 98 in 71% yield from 96. Amide 98 was then transformed into acrylamide 99 in... 

Scheme 19 Construction of key lactam 100 via two RCM steps and a zirconocene-mediated carbomagnesation in Martin s total synthesis of dihydrocorynantheol (101) [68]...

ChinkovM, Marek I (2005) Stereoselective Synthesis of Dienyl Zirconocene Complexes. 10 133-166... 

Negishi E, Tan Z (2005) Diastereoselective, Enantioselective, and Regioselective Carbo-alumination Reactions Catalyzed by Zirconocene Derivatives. 8 139-176 Netherton M, Fu GC (2005)Pa]ladium-catalyzed Cross-Coupling Reactions of Unactivated Alkyl Electrophiles with Organometallic Compounds. 14 85-108 Nicolaou KC, King NP, He Y (1998) Ring-Closing Metathesis in the Synthesis of EpothUones and Polyether Natmal Products. 1 73-104 Nishiyama H (2004) Cyclopropanation with Ruthenium Catalysts. 11 81-92 Noels A, Demonceau A, Delaude L (2004) Ruthenium Promoted Catalysed Radical Processes toward Fine Chemistry. 11 155-171... 

Szymoniak J, Bertus P (2005) Zirconocene Complexes as New Reagents for the Synthesis of Cyclopropanes. 10 107-132... 

In deciding on the material to be covered in this chapter, limitations had to be set. The first section will present the synthesis of various zirconocene hydrides. The focus of the subsequent sections is to present a general synopsis of the different aspects of the hydrozirconation reactions using 1 not only on carbon-carbon multiple bonds but also on heteropolar multiple bonds. Those aspects of hydrozirconation that were covered in previous reviews [1-5, 27] and in the excellent chapter by Labinger in Comprehensive Organic Synthesis [28] are summarized or briefly mentioned here. For other aspects of organozirconium chemistry not covered by the above-mentioned reviews, the reader is referred to a number of monographs and reviews [29, 30]. 

Scheme 8-4 Synthesis of zirconocene hydride Cp2Zr(H)OTf alternative to the Schwartz s reagent, ...

Note that the synthesis and reactivity of anionic [77, 78] and cationic [79] hydrido zirconocene(IV) complexes have been investigated but will not be addressed in this chapter. 

Titanocene catalysts do not catalyze the hydrosilation of most internal olefins, although they can attach active olefins such as styrene, or norbornene to the growing polymer chain ends. The zirconocene-based catalysts, on the other hand, can be powerful hydrosilation catalysts and the remarkable copolymer synthesis shown in Equation 3 can be easily achieved under mild conditions (V7). 

Mori reported an improved synthesis of (3S,4P,6 ,10Z)-faranal (37), the trail pheromone of the Pharaoh s ant (Monomorium pharaonis) [84]. As summarized in Scheme 55, the key-reaction was the coupling of iododiene A with iodide E. The geometrically pure A was prepared by the zirconocene-mediated carbo-alumination reaction, and E was prepared from B by the asymmetric cleavage of its epoxy ring to give C (77% ee), which could be purified via its crystalline 3,5-dinitrobenzoate D. 

Metallocene catalysis has been combined with ATRP for the synthesis of PE-fr-PMMA block copolymers [123]. PE end-functionalized with a primary hydroxyl group was prepared through the polymerization of ethylene in the presence of allyl alcohol and triethylaluminum using a zirconocene/MAO catalytic system. It has been proven that with this procedure the hydroxyl group can be selectively introduced into the PE chain end, due to the chain transfer by AlEt3, which occurs predominantly at the dormant end-... 

Negishi et al. reported the regioselective synthesis of diisoalkyl derivatives from monosubstituted alkenes in yields ranging from 58-95%, Scheme 8, from the in situ prepared ethylene complex Cp2Zr(C2H4).35 The zirconocene-ethylene complex presumably undergoes alkene insertion to furnish a zirconacyclopentane which further reacts with diethylzinc to yield the diisoalkylzinc compound. 

Collins S, Bailey L, Pigeon M (1998) Synthesis of elastomeric poly(propylene) using unsym-metrical zirconocene catalysts marked reactivity differences of rac - and meso -like dias-tereomers. Macromolecules 31 1000-1009... 

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