Trimethylenemethane complexes preparation

Cross-conjugated dienyltricarbonyliron cations have been prepared as follows from trimethylenemethane complexes [Eq. (22)] (186,187) ... 

Substituted trimethylenemethane complexes can be prepared from the appropriate reagents. In general, any substituents on the trimethylenemethane group direct the attached carbon to the /3-carbon of the acceptor alkene (equation 90). This directing effect is seen for both electron-donating and electron-withdrawing substituents. 

The trimethylenemethane complexes XLII and XLIII arise from dimerization. The parent 7f-allyl complex, XLIV, can be readily prepared from 3-chloro-2-(chloromethyl)-propene and Na tetracarbonylferrate - . Trimethylenemethane complexes of Mo and Cr are similarly prepared in low yield . ... 

JOM(322)103>. Other more exotic addition reactions of (55) have also appeared including reactions with allenes <90OM289> and phosphinimines <89JA7279,920M2613). The former reaction is an efficient method for the preparation of iron trimethylenemethane complexes. 

Another general way to prepare trimethylenemethane complexes is the reaction of trimethylenmethane dianions with metal halides. By this way. Mills et al. obtained (cyclopentadienyl)(trimethylenemethane)cobalt (21) in 18% yield by dilithiation of isobutene (19) with butyllithium/tetramethylethylenediamine (TMEDA) to dianion 20 [22,23] followed by treatment with 1 equiv. of (cyclopen-tadienyl)diiodo(triphenylphosphane)cobalt (Scheme 10.7). The crystal structure analysis shows a highly symmetric molecule with a slight pyramidalization of the trimethylenemethane ligand away from the cyclopentadienylcobalt... 

Cyclic Dienes. Ring opening of cis- and rrfl/is-2-phenylmethylene[3- Hi]-cyclopropane yields stereospecifically the trimethylenemethane complexes (82a, b), respectively the results are consistent with an allowed disrotatory ring opening, and are in agreement with frontier MO calculations. The exo-complex (83) and its enrfo-isomer have been prepared by reaction of the free... 

Methoxybutadiene has been complexed photochemically using Fe2(CO)9, instead of the more conventional thermal conditions. Complexation of acyclic dienes with Fe2(CO)9 constituted the first step toward trimethylenemethane complexes. All details concerning the preparation and spectral properties of tricarbonyl(butadiene)iron complexes are gathered in recent reviews. ... 

The presence of five-membered rings such as cyclopentanes, cyclopentenes, and dihydrofurans in a wide range of target molecules has led to a variety of methods for their preparation. One of the most successful of these is the use of trimethylenemethane [3 + 2] cycloaddition, catalysed by pal-ladium(O) complexes. The trimethylenemethane unit in these reactions is derived from 2-[ (trimethylsilyl)methyl]-2-propen- 1-yl acetate which is at the same time an allyl silane and an allylic acetate. This makes it a weak nucleophile and an electrophile in the presence of palladium(0). Formation of the palladium 7t-allyl complex is followed by removal of the trimethylsilyl group by nucleophilic attack of the resulting acetate ion, thus producing a zwitterionic palladium complex that can undergo cycloaddition reactions. 

Seven procedures describe preparation of important synthesis intermediates. A two-step procedure gives 2-(HYDROXYMETHYL)ALLYLTRIMETH-YLSILANE, a versatile bifunctional reagent. As the acetate, it can be converted to a trimethylenemethane-palladium complex (in situ) which undergoes [3 + 2] annulation reactions with electron-deficient alkenes. A preparation of halide-free METHYLLITHIUM is included because the presence of lithium halide in the reagent sometimes complicates the analysis and use of methyllithium. Commercial samples invariably contain a full molar equivalent of bromide or iodide. AZULENE is a fundamental compound in organic chemistry the preparation... 

Theoretical studies 225>226> as well as preparative work strongly indicate that the reactive palladium organic intermediate in Reaction 115b and 115c is an unsym-metrical, zwitterionic trimethylenemethane-palladium (TMM-Pd) complex, as formulated in Eq. 117. Moreover, cycloaddition with a cyclic TMM-Pd-precursor revealed that the electron-deficient olefin attacks the TMM-Pd unit from the side away from the metal. This demonstrates that complexation of the olefin with the metal does not occur prior to C—C bond formation 183>. 

Pd-catalyzed cyclization was also applied to the stereocontrolled preparation of chiral substituted tetrahydrofurans. The synthesis of optically active tetrahydrofurans was pioneered by Stork and Poirier,who described effective chirality transfer in the Pd-assisted cyclization of y-hydroxy allylic esters. Williams and Meyer deployed a variant of the 0-capture of 7r-allylpalladium complexes in the reactions of substimted trimethylenemethane palladium complexes developed by Trost, using aUylstannane (Scheme 32). A key intermediate 156 in the synthesis of amphidinolide K, a marine nam-ral product, was therefore synthesized starting from enantiopure diastereomer 160. Compound 160 was prepared by in situ transmetallation using the Corey chiral sulfonamide 159 with optically active aUylstannane 157 and then condensation with functionalized aldehyde 158. Formation of the c -2,5-disubstituted tetrahydrofuran 156 occurred with an excellent diastereoselectivity (cis/trans 13 1) and a good yield (88%) from the syn-1,4-precursor 160. 

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