Styrene chromium tricarbonyl

Alkyl radical addition reactions to styrene chromium tricarbonyl can be accomplished using alkyl halides (10 equiv) and (TMSlsSiH (5 equiv) in the presence of AIBN in refluxing benzene, for 18 h (Reaction 66). " These reactions are believed to proceed through intermediates in which the unpaired electron is interacting with the adjacent arene chromium tricarbonyl moiety since the analogous reaction with styrene affords only traces of addition products. 

The synthesis of tricarbonylchromium(O) complexes of mono-, di- and tri-substituted cyclopropanes, e.g. 150, has been accomplished through the reaction of tricarbonyl(styrene) chromium(O) complexes 151 with phosphorus and sulfur ylides. ... 

Table 4. Asymmetric Hydroformylation of" Styrene and Tricarbonyl(styrene)chromium... 

Similar cross-coupling procedures have been used to prepare styrenes by the reaction of metalated aromatics with vinyl halides/triflates or, conversely, metalated alkenes with aromatic halides/triflates in the presence ofPd(Ph3P)4 (eq 6). Typically, ArCl are poor substrates in Pd(PPh3)4-catalyzed coupling reactions. However, by forming the chromium tricarbonyl complex of the aryl chloride, a facile coupling reaction with vinyl-stannanes can be achieved (eq 7). ... 

Activation of the Benzylic Position. Both chromium com-plexed carbanions and carbocations are stabilized at the benzylic position. Dialkylation of alkyl halides at the benzylic position occurs via stabilized carbanions under mild conditions (eq 16). Regio- and stereoselective products are obtained via the benzylic carbanions, depending on the conformation of the tricarbonyl group to the arene (eq 17). (Styrene)chromium complexes stabilize negative charges at the benzylic position by addition of... 

Mukai et al. (36,37) applied the chiral tricarbonyl(r -arene)chromium(0)-derived nitrone 24b in 1,3-dipolar cycloadditions with various alkenes, such as styrene 25 (Scheme 12.11). The analogous nonmetallic nitrone 24a was used in a reference reaction with 25, giving the isoxazohdine 26a with an endo/exo ratio of 82 18. By the apphcation of nitrone 24b in the 1,3-dipolar cycloaddition with 25, the endo/exo-selectivity changed significantly to give exo-26b as the only observable product. The tricarbonylchromium moiety effectively shielded one face of the nitrone, leading to high diastereofacial selectivity. The product exo- 26b was obtained with 96-98% de. 

Other polymers which have been the subject of thermal degradation studies include ethylene-vinyl acetate [29, 66, 67], ethylene-vinyl alcohol [68], poly(aryl-ether ketone) [69], poly-2-vinyl-naphthalene-co-methyl maleate [34], polyphenylenes based on diethyl-benzophenone [70], polyglycollide [71-73], poly(a-methylstyrene tricarbonyl chromium [74], polytetrahydrofuran [75], polylactide [76-78], poly(vinyl) cyclohexane [79], styrene-vinyl cyclohexane [80], isopropenylacetate-maleic dianhydride [80], polyethylene glycol containing a 1,3-disubstituted phenolic group [81], poly-2-vinyl naphthalene-co-methacrylate [34], collagen biopolymers [82], chitin graft poly (2-methyl-oxazoline - polyvinyl chloride blends [83], cellulose [32, 83-88] and side-chain cholestric elastomers [89, 90]. 

Various strategies for the synthesis of metallocene monomers were described in [198]. Vinylmetallocenes 38 like vinylferrocene or ri -(vinylcyclopentadienyl)-dicarbonylnitro-sylmanganese 39 are prepared several decades ago by synthesizing the vinyl group in the metallo-derivatives [199]. Other 7c-type compounds such as ri -(styrene)tricarbonyl-chromium 40 are obtained by reaction of styrene with triamine-tricarbonylchromium [200]. 

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