Norbomenes synthesis

Lipase-catalyzed enantioselective transesterification of 0-substituted-l,2-diols is another practical route for the synthesis of P-blockers. Lipase PS suspended in toluene catalyzes the transesterification of (63) with vinyl acetate to give the (5)-ester in 43% yield and >98% ee (78). The desired product, optically pure (R)-ttitylglycidol, is then easily obtained by treating the ester with alcohoHc alkaU. Moreover, Pseudomonas Hpase catalyzes the acylation of oxazohdinone (64) with acetic anhydride in very good yield and selectivity (74). PPL-catalyzed transesterification of a number of /n j -norbomene derivatives proceeds in about 30% yield and 92% ee (79,80). 

A somewhat more complex application of this notion is represented by the CNS stimulant fencamfine (83). Diels-Alder addition of cyclopentadiene and nitrostyrene affords the norbomene derivative, 80. Catalytic hydrogenation reduces both the remaining double bond and the nitro group (81). ° Condensation with acetaldehyde gives the corresponding imine (82) a second reduction step completes the synthesis of fencamfine (83). ... 

Table 1 Postulated reaction mechanism for the synthesis of norbomene...

The kinetic parameters associated with the synthesis of norbomene are determined by using the experimental data obtained at elevated temperatures and pressures. The reaction orders with respect to cyclopentadiene and ethylene are estimated to be 0.96 and 0.94, respectively. According to the simulation results, the conversion increases with both temperature and pressure but the selectivity to norbomene decreases due to the formation of DMON. Therefore, the optimal reaction conditions must be selected by considering these features. When a CSTR is used, the appropriate reaction conditions are found to be around 320°C and 1200 psig with 4 1 mole ratio of ethylene to DCPD in the feed stream. Also, it is desirable to have a Pe larger than 50 for a dispersed PFR and keep the residence time low for a PFR with recycle stream. 

Another example of this useful domino process is the enantioselective synthesis of the quinozilidine alkaloid (-)-lasubine II [234]. Condensed tricyclic compounds as 6/3-28 can also be prepared from norbomene derivatives 6/3-27 in excellent yield, as shown by Funel and coworkers (Scheme 6/3.6) [235]. 

Further important industrial applications of olefin metathesis include the synthesis of 3,3-dimethyl-l-butene ( neohexene , intermediate for the production of musk perfume) from ethene and 2,4,4-trimethyl-2-pentene, the manufacture of a,co-dienes from ethene and cycloalkenes (reversed RCM), and the ROMP of cyclooctene and norbomene to Vestenamer and Norsorex , respectively. 

The most common alkenes employed in the Pd-catalysed synthesis of alternating polyketones are ethene, styrene, propene and cyclic alkenes such as norbomene and norbornadiene. Even though the mechanism does not vary substantially with the alkene, the reactions of the various co-monomers are here reported and commented on separately, starting with the ethene/CO copolymerisation, which is still the most studied process. As a general scheme, the proposed catalytic cycles are presented first, then the spectroscopic experiments that have allowed one to elucidate each single mechanistic step. 

The metathesis route opens up new opportunities for the synthesis of new copolymers by copolymerizing 6,7-dihydro-2(3//)-oxepinone with other cyclic olefins such as norbomene, even though this approach has barely been exploited until now [121]. 

Research Focus Synthesis of curable poly(ethylene-co5-ethylidene-2-norbomene) copolymers using a catalyst pair consisting of iron and zirconium metal complexes. 

W. Wang and K. Nomura, Remarkable effects of aluminum cocatalyst and comonomer in ethylene copolymerizations catalyzed by (arylim-ido)(aryloxo) vanadium complexes efficient synthesis of high molecular weight ethylene/norbomene copolymer, Macromolecules, 38(14) 5905-5913, July 2005. 

Numerous aziridines have been prepared by triazoline photolysis it is the principal route to the synthesis of N-arylaziridines. Photolysis of triazolines derived from simple79,113,144 and cyclic79,87,113 olefins as well as norbomene... 

This method is applicable to the efficient synthesis of 2,5-norbomadiene, which can be obtained in low yield by anodic decarboxylation of 5-norbomene-2,3-dicarboxylic acid (equation 43)47. 

Synthetic protein-like polymers containing amino acids find pharmaceutical and biological applications and display self-assembly properties [174], In this aspect, both ROMP and ADMET have been used as tools for the polymerization of amino acid-based monomers. Early ROMP examples date back to 1994 with the synthesis and ROMP of amino acid-derived homochiral norbomene monomers by Coles et al [175], The molybdenum complex [Mo(=CHCMe2Ph)(=NC6H3Pr,2-2,6)(OBu )2]... 

Scheme 24 Synthesis of random and block copolymers via ROMP of amino acid-functionalized norbomenes [173]...

CONTENTS Preface, Brian Hatton. Applications of Ring Strain in Natural Product Synthesis, James D. White and Nadine Chauyi Lee. Uses of the Vacuum Gas-Solid Reaction Procedure in Synthesis, W. E. Billups and Benny E. Amey, Jr. Polysubstituted Cubanes Towards Complete Systematic Substitution of the Cubane Nucleus, John Tsanaktsidis. A Personal Perspective on Norbomenes, Cyclobutenes, and Other Ring-Strained Dienophiles in Organic Synthesis, Ron N. Warrener. Synthetic Studies Related to Fullerenes and Fullerene Fragments, Goverdhan Mehta and H. Surya Prakash Rao. Index. 

Copper-catalyzed [2 + 2] photocycloadditions are related to the latter reactions. These transformations have been extensively studied, frequently in the context of application to organic synthesis [21], When irradiated in the presence of copper(I) triflate, norbomene 12 was effidently transformed into its dimer 13 (Scheme 5.3, reaction 4) [22]. Although complexes such as III are involved in the reaction mechanism [22, 23], it is unclear whether MLCT (metal to ligand charge transfer) or LMCT (ligand to metal charge transfer) excitation induces the transformation. 

These complexes are suitable for the ring-opening metathesis polymerization of functionalized norbomenes in water,148 as well as ring-closure reactions via ethylene elimination.149 The versatility of these catalysts has given rise to extensive applications in organic synthesis,150151 including, for example, amino acid derivatives.152... 

Compound 1 did not react with unstimned internal olefins such as tetramethylethylene, /ra s-3-hexene, tram-stilbene, cyclooctene, cyclohexene, or cyclopentene. But imposing strain to the olefinic moiety resulted in a clean silylene transfer to the double bond Norbomene formed with 1 the tricyclic silacyclopropane 6. Whereas 2 did not add to the double bond of 7, methylene cyclopropane 8 could be transformed into spiro[2.2]pentane 9 by reaction with 1. Addition of 2 to bicyclopropylidene allowed the convenient synthesis of dispiro[2.0.2.1]heptane 10 in a quantitative manner. 

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