Allylic molybdenum

Asymmetric nucleophilic addition of Jt-allyl molybdenum complex as the final route. 

An intermediate proposed to occur during the ammonoxidation of propene and that would correspond to the intermediate B suggested for the oxidation of propene is B as shown in Scheme 1. Compounds designed to model these intermediates structurally or functionally should contain a 7r-allyl-molybdenum group covalently bound to an imido ligand as a minimum requirement, ideally an 0x0 ligand should be bound in addition. 

The (IsQ-coordinated species [Mo(CO)3(py)3] prepared from [Mo(CO)6] and pyridine is useful for the synthesis of various jr-allyl molybdenum compounds (68JOM(13)Pl, 970M5365). The 3-allyl complexes [( 3-allyl)Mo(CO)2Br(py)2] form [( 3-allyl)Mo(CO)2(S,S)(py)] with the anionic S,S-donors, dithiocarbamates and xanthates of sodium and potassium, M (S,S) (81JOM(218)185). [( 3-C3H5)Mo(CO)2(py)2Br] (68JO M(14)375) with thallium hexafluorophosphate in acetonitrile gives... 

By this route rc-allyl molybdenum compounds are obtained in good yields ... 

Finally, the use of stoichiometric amounts of transition metal complexes can play an important role in the synthesis of functionalized piperidines. <01H14.39> Liebeskind and coworkers have developed a chiral transition metal complex and have used it in the synthesis of (-)-indolizidine 209B <01JA12477>. A lipase mediated allylic alcohol resolution provides access to both antipodes of enantiomerically pure allyl acetates (115) which can be used to form an ri -allyl molybdenum complex (116), Hydride abstraction followed by methoxide quench yields a reactive species 117 which may be further functionalized through reactions with Grignard reagents. The eventual products 119 arc 2,3,6-trisubstituted piperidines in enantiomerically pure form. 

Several molybdenum derivatives can be prepared using a thiolate. A stable monomeric 7r-allyl molybdenum derivative has been obtained by the metathesis ... 

Cl 5H1 gin, Tris(cyclopentadienyl) indiumdil), 38B, 700 Cl5H17GaMoNg02, Dicarbonyl(methyltris(1-pyrazolyl)gallato)(t -allyl)molybdenum, 44B, 665... 

Other initiators that have been used for AN polymerization include trivalent phosphorous compounds dialkylaminotita-nium, allyl molybdenum, and tungsten compounds and metal-free ammonium salts of malonates and carbazo-lides. ° °° ° All of these initiators produce PAN less efficiently with varying degrees of molecular weight and MWD control. The side reactions can be classified as given in... 

The complexes (ji-C3H5)2M may be assumed to have a sandwich structure as found for bis-jr-2-methyl allyl nickel. Preliminary X-ray studies of tetrakis-2r-allyl molybdenum suggest that there are three... 

Wlien tlie diiral molybdenum -K-allyl-substituted enone 147 was treated witli litliium dimetliylciiptate, formation of adduct 148 witli fait selectivity was observed tSdieme 6.29) [69], Interestingly, bigber selectivities were obtained in tlie presetice of boron ttlbuotlde etlierate. It is assumed tliat Lewis acid coordination induces tlie s-trans reactive conformation 149 [64], Consequently, nudeopb de attack anti to tlie molybdetiLim ftagmetit sbould afford tlie major diastereomer 148. 

Midiael aooeptois octended 146ff misopnostol 72 Mitsunobii leaction 292f molybdenum allyl oomplexes... 

Most preparations of the intermediate racemic 3-allyl(dicarhonyl)cyclopentadieny molybdenum complexes7 2 start from sodium or potassium tricarbonyl(cyclopentadienyl)molybdate8 9 10 (4) for a simple preparation see ref 11, p 493. The allylation of 4 hy homoallylic halides, such as 4-hromo-l-butene, is accompanied by rearrangement and decarhonylationI2. (Z)-if-2-butenyl(dicarbonyl)cyclopentadienylmolybdenum (5), like other comparable complexes, exists as a mixture of endo/exo- conformers, which interconvert rapidly at room temperature12. 

Allyl(dicarbonyl)molybdenum complexes 5 are also prepared from 4 via the methyl derivative... 

Stable enolates such as diethyl malonate anions react with allyl sulfones (or acetates) in the presence of nickel complexes to give a mixture of the a- and /-product83. The regioselectivity is generally poor in the nickel-catalyzed reaction, but the molybdenum-catalyzed reaction is selective for alkylation at the more substituted allylic site, thereby creating a quaternary carbon center84. 

The alkylation of allylic sulfides with stable anions takes place by using stoichiometric amounts of molybdenum hexacarbonyl86. Contrary to the catalytic reaction, the C —C bond formation occurs at the less hindered site of allyl groups in the stoichiometric reaction. 

Molybdenum, tris(phenylenedithio)-structure, 1,63 Molybdenum alkoxides physical properties, 2,346 synthesis, 2,339 Molybdenum blue liquid-liquid extraction, 1,548 Molybdenum cofactor, 6,657 Molybdenum complexes acrylonitrile, 2,263 alkoxides, 3,1307 alkoxy carbonyl reactions, 2,355 alkyl, 3,1307 alkyl alkoxy reactions, 2,358 alkyl peroxides oxidation catalyses, 6,342 allyl, 3,1306... 

Treatment of bis(pyridine) complexes of molybdenum and tungsten, M(f/ -allyl)Cl(CO)2(py)2 (M = Mo, W) with equimolar amounts of lithium amidinates Li[RC(NPh)2] (R = H, Me) afforded amidinato complexes of the type M(r -allyl)[RC(NPh)2](CO)2(py) (M = Mo, W). Reactions of the latter with acetonitrile, PEts, and P(OMe)3 have been investigated Free amidines react with M(r -allyl)Cl(CO)2(NCMe)2 according to Scheme 124 to give the corresponding bis(amidine) complexes. ... 

Allylic acetates give dienes when heated with certain palladium or molybdenum compounds. 

Chiral pyridine-based ligands were, among various Ar,AT-coordinating ligands, more efficient associated to palladium for asymmetric nucleophilic allylic substitution. Asymmetric molybdenum-catalyzed alkylations, especially of non-symmetric allylic derivatives as substrates, have been very efficiently performed with bis(pyridylamide) ligands. 

Trost and Hachiya [140] studied asymmetric molybdenum-catalyzed alkylations. Interestingly, they noticed that the regioselectivity of this transformation performed with a non-symmetric allylic substrate varied according to the nature of the metal Pd-catalyzed substitutions on aryl-substituted allyl systems led to attack at the less substituted carbon, whereas molybdenum catalysis afforded the more substituted product. They prepared the bis(pyridylamide) ligand 105 (Scheme 55) and synthesized the corresponding Mo-complex from (C2H5 - CN)3Mo(CO)3. With such a catalyst, the allylic... 

The partial oxidation of propylene occurs via a similar mechanism, although the surface structure of the bismuth-molybdenum oxide is much more complicated than in Fig. 9.17. As Fig. 9.18 shows, crystallographically different oxygen atoms play different roles. Bridging O atoms between Bi and Mo are believed to be responsible for C-H activation and H abstraction from the methyl group, after which the propylene adsorbs in the form of an allyl group (H2C=CH-CH2). This is most likely the rate-determining step of the mechanism. Terminal O atoms bound to Mo are considered to be those that insert in the hydrocarbon. Sites located on bismuth activate and dissociate the O2 which fills the vacancies left in the coordination of molybdenum after acrolein desorption. 

---