Allyl derivatives, characterization

In an effort to prepare a a-bonded allyl derivative analogous to Cp UCLHij, Tsutsui and Ely (38) prepared Cp2LnC Hc (Ln=Sm,Er, Ho) by reacting Cp LnCl with allylmagnesium bromide in THF-ether solution at -7o°C. Characterization of these new allyl deri-... 

The regio- and stereoselectivity of many catalytic reactions that involve nucleophilic attack on T-allyl palladium intermediates are determined by the structure and conformation of these complexes in the reaction medium. For this reason, much effort has been devoted to the determination of the structures of 77 -allylic palladium complexes not only in the solid state but also in solution. X-ray, theoretical, and NMR tools have been developed and used together, so it is now possible to completely characterize a palladium 7 -allylic derivative and explain the factors that control the stability of the preferred structure. ... 

Many complexes have been studied by this combination of techniques, especially 77 -allyl derivatives with chiral auxiliary ligands, such as phosphines,diphosphines, " A jP-donors, and N,N-These ligands are characterized by their large size that sufficiently intrudes in the allylic coordina-... 

Reaction of (chloromethyl)allyl chloride with NaCo(CO)4 snelds the allyl derivatives (33) and (34), both characterized crystallographically [(34) as its P(OMe)3 substitution product]. ... 

The (pentamethylcyclopentadienyl)zirconium amidinate unit also served as a platform for the synthesis and characterization of remarkable cationic and zwitterionic allyl zirconium complexes derived from trimethylenemethane (TMM). A direct synthetic route to the neutral precursors was found in the... 

Helquist et al. [129] have reported molecular mechanics calculations to predict the suitability of a number of chiral-substituted phenanthrolines and their corresponding palladium-complexes for use in asymmetric nucleophilic substitutions of allylic acetates. Good correlation was obtained with experimental results, the highest levels of asymmetric induction being predicted and obtained with a readily available 2-(2-bornyl)-phenanthroline ligand (90 in Scheme 50). Kocovsky et al. [130] prepared a series of chiral bipyridines, also derived from monoterpene (namely pinocarvone or myrtenal). They synthesized and characterized corresponding Mo complexes, which were found to be moderately enantioselective in allylic substitution (up to 22%). 

Similar reactions occur with all aliphatic halides and the rates of substitution are related to the degree of ionic character of the carbon-halogen bond. For preparation purposes, trityl bromide or propargyl bromide are more convenient than allyl bromide. The compounds obtained are listed in Table XI. They were obtained pure and characterized fully. Zr (allyl) 3Br and Zr(allyl)2Br2 are sufficiently soluble in toluene for polymerizations to be initially homogeneous. Their relative reactivities are listed in Table XI. In all cases hydrogen was used to reduce the molecular weight of the polymer formed. In this respect the polymer derived from Zr (allyl )3Br was more readily modified than that from Zr (allyl) 4, but in order to avoid... 

The parent compound, 69, has been synthesized and characterised <2003ZFA1475>. 4-Chloro-hepta-l,6-diene was reacted with Mg. No Grignard rearrangement was noticed but instead the Grignard reagent was converted into l-allyl-3-butenylphosphonous dichloride by reaction with PC13. Reduction with LiAlH. produced l-allyl-3-butenyl-phosphane. Radical-initiated cyclization led to the product, l-phosphabicyclo[3.3.0]octane. Four derivatives were similarly prepared and characterized (70-73). Compound 74 was similarly prepared via a radical reaction < 1997PS(123)141 >. 

The transition metal-catalyzed allylic substitution using hard or unstabilized nucleophiles has not been extensively studied, particularly with unsymmetrical allylic alcohol derivatives. This may be attributed to the highly reactive and basic nature of these nucleophiles and the inability to circumvent regiochemical infidehty in unsymmetrical systems. Hard nucleophiles may be characterized as those that undergo substitution with net inversion of stereochemistry [29], due to their propensity to add directly to the... 

The allyl cation has never been characterized as a persistent species in solution. If prepared, it would be the smallest carbenium ion universally accepted to have been formed in condensed media (this title has for many years been held by the isopropyl cation). No allyl cation derivatives, e.g., 10, were observed in a 1990 report of a CAVERN study of butadiene on HY and HZSM-5 (104). The same year, Hutchings reported a flow reactor study of allyl alcohol on HZSM-5 (105) and Gorte (106) reported a TPD study of allyl alcohol on the same zeolite. Hutchings and co-workers found that allyl alcohol had two reaction paths, one in which propanal was formed and another that formed hydrocarbons. The latter route was proposed to proceed through an allyl cation intermediate, but no claim for its persistence or spectroscopic observation was made or implied by Hutchings. Gorte... 

Characterization of the essential oils of onion and garlic was aided by the isolation of silver derivatives. The salts containing n-propanethiol and allyl thiol were both insoluble and could not be recrystallized.296... 

---