Allylic crystal structure

A crystal structure of the C02 derivative of (8), K[Co(salen)( 71-C02)], haso been reported in which the Co—C bond is 1.99 A, the C—O bonds are both equivalent at 1.22 A and the O-C-O angle is 132°.125 Carboxylation of benzylic and allylic chlorides with C02 in THF-HMPA was achieved with (8) electrogenerated by controlled-potential electrolysis,126 in addition to reductive coupling of methyl pyruvate, diethyl ketomalonate and / -tolylcarbodiimide via C—C bond formation. Methyl pyruvate is transformed into diastereomeric tartrates concomitant with oxidation to the divalent Co(salen) and a free-radical mechanism is proposed involving the homolytic cleavage of the Co—C bond. However, reaction with diphenylketene (DPK) suggests an alternative pathway for the reductive coupling of C02-like compounds. 

The crystal structure of (232) is reported. Ir complexes bound to the multidentate ligand as in (232) have proved successful in the enantioselective reduction of a,/3-unsaturated ketones to allylic alcohols.404... 

The late stages of the synthesis (Scheme 1.17) proceeded with Wittig methylenation of ketone 144 with Ph3P=CH2 at 70 °C to furnish exocyclic alkene 145 in 77 % yield. Finally, the alcohol was installed via a Se02-mediated allylic hydroxylation [57] of the exocyclic alkene 145 to afford ( )-nominine (1) in 66 % and 7 1 dr. The structure of nominine (1) was verified via an X-ray crystal structure determination, thereby completing the racemic total synthesis of ( )-nominine (1). 

Scheme 10. Results of proline-copper catalyzed allylic oxidation, prom (105).] X-ray crystal structure of (R.Sf-complex 146. [Adapted from (106).]...

A model accounting for the observed sense of absolute stereoinduction is based upon the coordination mode revealed in the crystal structure of the cyclometallated C,0-benzoate complex [280]. It is postulated that aldehyde binding by the a-allyl haptomer occurs such that the allyl moiety is placed between the naphthyl and phenyl moieties of the hgand, allowing the aldehyde to reside in a more open enviromnent. In the favored mode of addition, the aldehyde C-H bond projects into... 

The preparation of (jr-allyl)(PHOX)Ir complexes was possible by using standard methods. A typical example is depicted by a crystal structure in Figure 9.1. Here, the configuration around the Ir center is as to be expected on the basis of the trans influences of the ligands. The reaction of this complex with dimethyl sodiomalonate proceeds by ligand exchange and addition of the nucleophile at the... 

The next landmark was the synthesis of the germylium, 22, and the stannylium ion, 23, by one-electron oxidations from the corresponding stable radicals with trityl TPFPB by Sekiguchi and co-workers. As in the case of the allyl cleavage to generate the mesityl-substituted cations, the reaction, in this case the oxidation, occurs at the periphery of the molecule and gives the possibility for efficient steric protection of the incipient cation. Both trivalent cations were obtained as their TPFBP salts and the crystal structure show well separated anions and cations. 

Bis[(dimethylisopropoxysilyl)methyl]zinc (74) has proven to be a valuable reagent in the nickel-catalysed cross-coupling reactions with alkenylsulfoximines, giving allylic silanes with complete retention of configuration. An X-ray crystal structure determination of 74 showed this compound to exist in the solid state as a coordination polymer (Figure 41). In 74, in addition to the two covalent Zn—C bonds [Zn—C(l) 1.953(7)... 

A number of isocyanide complexes, [Mo(CN)4(CNR)4] (R = Me, Pr, Bu allyl, NCPh2), have been made by the action of RI on Ag4[Mo(CN)8]. The crystal structure of [Mo(CN)4(CNMe)4] shows a dodecahedral geometry, with the CN- ligands at 2.177(8) A and the MeNC ligands at 2.148(8) A from the molybdenum.207 Both 13C NMR and vibrational spectroscopy indicate that only one isomer is present in solution. 

Crystal structures of the benzotriazole complexes [Zn(HL)Cl2] and [Zn2L4] (HL = benzotriazole 62) have been reported the former compound has the metal in a tetrahedral N2C12 environment (Zn—N, 2.014, 2.034 A Zn—Cl, 2.241, 2.235 A) and the latter is a polymeric species.441 The complex [H2L]2[ZnCU] (HL = 62) has also been described it is isostructural with the tetrachlorocobaltate(II) analogue, which has previously been structurally characterized.441 The synthesis and powder diffraction pattern for [ZnL Cy (L = 62) have also been reported.442 Complexes of the type MX2L2 (M - Zn, X = Cl, Br, I or SCN M = Cd, X = Cl L = allyl or 3,5-dimethylpyrazole) have been synthesized where L is 3,5-dimethylpyrazole, cadmium also forms the complexes (CdBr2L3 and CdI2L4. When L is allylpyrazole, alkene coordination is not observed thiocyanate is N-bonded.443,444... 

Interestingly, treating (>/4-cyclooctatetraene)Fe(CO)3 with acetyl chloride under Friedel-Crafts reaction conditions yielded unexpectedly222-223 the (>/2,>/3-8-e.x0-acetyl bicy-clo[3.2.1]octadienylium)Fe(CO)3 cation complex, presumably by rearrangement of the intermediate bicyclo[5.1.0]octadienylium isomer (Scheme 8). The structure of the rearranged cation was confirmed from the X-ray crystal structure and from the typical 1,3-cr.ji-allylic products obtained upon nucleophilic reaction with LiAlD4 and NaCN. The nucleophilic reaction of the more bulky iodide occurs, however, on the metal. 

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