Cyclohexene Lewis acid-base reaction

For example, draw the Lewis acid-base reaction between eyelohexene and H-Cl. The Brpnsted-Lowiy acid HCI is also a Lewis acid, and cyclohexene, having a n bond, is the Lewis base. 

The Lewis acid-base reaction of cyclohexene with HCI is a specific example of a fundamental reaction of compounds containing C-C double bonds, as discussed in Chapter 10. 

Chlorine alone does not react with benzene, in contrast to its instantaneous addition to cyclohexene. However, in the presence of a Lewis acid catalyst, such as ferric chloride or aluminum chloride (Section 4.7), benzene reacts with chlorine to give chlorobenzene and HCl. As shown in the following mechanism, this reaction involves a series of Lewis acid/base reactions. 

Cationic organozinc compounds are expected to be good catalysts for ring opening polymerization reactions of epoxides and lactones because the enhanced Lewis acidity (see Lewis Acids Bases) of the zinc center favors its coordination to the monomer. For example, Walker and coworkers have found that the cationic zinc substituted cyclopentadienyl complex [3,5-Me2C6H3CH2CMe2C5H4Zn(TMEDA)]+ [EtB(C6F5)3] is an active initiator species for the polymerization of cyclohexene oxide and e-caprolactone. ... 

The reaction of cyclohexene oxide with aryllithium reagents in the presence of both a Lewis acid (BFj OEy and a Lewis base (sparteine) provides the ring opened product in excellent yields with moderate enantioselectivity <05EJO1354>. Reaction always occurs at the (5)-carbon of the oxirane. Other meso-epoxides gave excellent yields but with a lower enantioselectivity. 

The metal-based Lewis acid derived from the camphor-derived Kgands such as (7.159) and La(OTf)3 is effective in the MBH reaction of aromatic aldehydes with a,P-unsaturated aldehydes mediated by l,4-diazabicyclo(2.2.2]octane (DABCO). The best ees (up to 95%) are obtained using sterically bulky acrylates such as a-naphthyl acrylate. More success has been obtained using Bronsted acidic organocatalysts. The partially reduced BINOL (7.160) has been used to effect enantioselective MBH reaction of aliphatic aldehydes such as (7.71) with 2-cyclohexen-l-one (7.161) mediated by triethylphosphine/ while bis(thio)ureas such as (7.163) provide up to 96% ee in the coupling of this ketone with cyclohex-anecarbaldehyde in the presence of DABCO. °... 

The oxide catalysts are microporous or mesoporous materials or materials containing both types of pores. In the latter case, the applicability is larger in terms of the molecular size of the reactants. Acid-base properties of these materials depend on the covalent/ionic character of the metal-oxygen bonds. These sites are involved in several steps of the catalytic oxidation reactions. The acid sites participate with the cation redox properties in determining the selective/unselective catalyst behavior [30,31]. Thus, many studies agree that partial oxidation of organic compounds almost exclusively involves redox cycles and acid-base properties of transition metal oxides and some authors have attempted to relate these properties with activity or selectivity in oxidation reactions [31,42]. The presence of both Bronsted and Lewis acid sites was evidenced, for example, in the case of the metal-modified mesoporous sihcas [30,39,43]. For the bimetallic (V-Ti, Nb-Ti) ions-modified MCM-41 mesoporous silica, the incorporation of the second metal led to the increase of the Lewis sites population [44]. This increased concentration of the acid sites was well correlated with the increased conversion in oxidation of unsaturated molecules such as cyclohexene or styrene [26,44] and functionalized compounds such as alcohols [31,42] or phenols [45]. 

In addition to boron-based Lewis acids, some transition metal complexes have been shown to be able to polymerize diazomethane [20, 21]. For example, Werner and Richards reported that nickelocene was highly active for polymerization of diazomethane, and proposed a polymerization mechanism where a propagating chain end contained a Ni-C bond as an active species [21]. On the other hand, when they examined a reaction of nickelocene with ethyl diazoacetate (EDA) in cyclohexene, no polymer was formed but diethyl fumarate, diethyl maleate, and ethyl norcaranecarboxylate were obtained in a 1.4 2.6 1.0 ratio (Scheme 6). 

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