Pentenes oxidation

Finally, metalated epoxides undergo isomerization processes characteristic of traditional carbenoids (Scheme 5.2, Path C). The structure of a metalated epoxide is intermediate in nature between the structures 2a and 2b (Scheme 5.2). The existence of this intermediacy is supported by computational studies, which have shown that the a-C-O bond of oxirane elongates by -12% on a-lithiation [2], Furthermore, experimentally, the a-lithiooxycarbene 4a (Scheme 5.3) returned cydo-pentene oxide 7 among its decomposition products indeed, computational studies of singlet 4a suggest it possesses a structure in the gas phase that is intennediate in nature between an a-lithiocarbene and the lithiated epoxide 4b [3],... 

Pentene oxidation over TS-1 catalyst is a fast reaction and hence fulfils a basic requirement for being suited to micro-channel processing [30]. Thus, it can serve as a model reaction to demonstrate the benefits of micro chemical engineering, particularly for zeolite-catalyzed reactions. Apart from this, epoxidations are an important class of organic reactions, also of industrial importance. 

A highly effective catalytic method for alkynylation of epoxides has recently been reported this involves the chelation-controlled alkylation of hetero-substituted epoxides with Mc3A1 and alkynyllithiums via pentacoordinate organoaluminum complexes [82]. For instance, reaction of epoxy ether, (l-benzyloxy)-3-butene oxide (75) in toluene with PhC = CLi under the influence of catalytic MesAl (10 mol%) proceeded smoothly at 0 °C for 5 h to furnish the alkynylation product l-(benzyloxy)-6-phenylhex-5-yn-3-ol (76) in 76 % yield. The yield of the product was very low (3 %) without MeaAl as catalyst under similar conditions. This is the first catalytic procedure for amphiphilic alkylation of epoxides. The participation of pentacoordinate MesAl complexes of epoxy ethers of type 75 is emphasized by comparing the reactivity with the corresponding simple epoxide, 5-phenyl-l-pentene oxide (77), which was not susceptible to nucleophilic attack of PhC s CLi with catalytic Me3Al under similar conditions (Sch. 50). 

In our previous studies [13], we have found the product distribution and the anhydride yields to be a strong function of reduction temperature in 1-pentene oxidation reaction. Table 1 summarizes the yields of major reaction products over the pre-reduced vanadia catalysts at different reduction and reaction temperatures. Only the results from the unpromoted catalysts are included in this table. The yield, for any product A is defined as... 

According to this expression, at 50°C the value of [ROOH] for cyclo-pentene oxidation where this maximum rate is obtained is 9.0 M or at about 82% conversion of the cyclopentene. Such a conversion is practically unattainable because other reactions of the hydroperoxide become important as its concentration increases. However, for less reactive hydrocarbons where kp/(2kt)in is only 0.01—0.1 that for cyclopentene, the maximum hydroperoxide concentration (0.5—3.0 M) is lower and the limiting rate is obtainable. 

The intramolecular oxidative earbonylation has wide synthetie applieation. The 7-lactone 247 is prepared by intramolecular oxycarbonylation of the alke-nediol 244 with a stoichiometric amount of Pd(OAc)2 under atmospheric pres-sure[223]. The intermediate 245 is formed by oxypalladation, and subsequent CO insertion gives the acylpalladium 246. The oxycarbonylation of alkenols and alkanediols can be carried out with a catalytic amount of PdCl2 and a stoichiometric amount of CuCb, and has been applied to the synthesis of frenolicin(224] and frendicin B (249) from 248[225]. The carbonylation of the 4-penten-l,3-diol 250, catalyzed by PdCl2 and CuCl2, afforded in the c -3-hydroxytetrahydrofuran-2-aeetie acid lactone 251[226J. The cyclic acetal 253 is prepared from the dienone 252 in the presence of trimethyl orthoformate as an accepter of water formed by the oxidative reaction[227]. 

FIGURE 6 11 The oxidation phase in the hydroboration-oxidation of 1 methylcydo pentene... 

Mesityl Oxide. Mesityl oxide (MSO) (4-metliyl-3-penten-2-one) is an oily colorless liquid with an unpleasant odor. It exhibits the versatiUty and unusual reactivity associated with conjugated a,P unsaturated carbonyl compounds (172). On standing ia air, mesityl oxide slowly forms bis(3,5,5-trimethyl-l,2-dioxolanyl)-3-peroxide (173). 

Commercial mesityl oxide can contain 5—20% of the P,y-unconjugated isomer isomesityl oxide [141-79-7] (4-meth5l-4-pentene-2-one). At equihbrium, the mixture contains 91% of the a,P-mesityl oxide and 9% of the P,y-isomer (174—176). Kquilihrium is cataly2ed by either acid or alkaU. Techniques to isolate the isomers have been reported (174,176), and some physical properties of isomesityl oxide are reported ia Table 1. 

Methyl-1-pentene [691-37-2] is alight, colorless, flammable fiquid its physical constants are also given in Table 1. It is an irritant and, in high concentrations, a narcotic. Like 1-butene, this chemical compound has a low flash point and represents a significant fire hazard when exposed to heat, flame, or oxidizing agents. 

Propylene oxide is a colorless, low hoiling (34.2°C) liquid. Table 1 lists general physical properties Table 2 provides equations for temperature variation on some thermodynamic functions. Vapor—liquid equilibrium data for binary mixtures of propylene oxide and other chemicals of commercial importance ate available. References for binary mixtures include 1,2-propanediol (14), water (7,8,15), 1,2-dichloropropane [78-87-5] (16), 2-propanol [67-63-0] (17), 2-methyl-2-pentene [625-27-4] (18), methyl formate [107-31-3] (19), acetaldehyde [75-07-0] (17), methanol [67-56-1] (20), ptopanal [123-38-6] (16), 1-phenylethanol [60-12-8] (21), and / /f-butanol [75-65-0] (22,23). 

Methyl-2-penten-4-one (mesityl oxide) Treatment of 9.8 g (0.1 mole) of the ketone by the above procedure gives on distillation 6.6 g of methyl isobutyl ketone, bp 117-1187I atm and a residue of 3 g. 

A convenient synthesis of 5-(methoxymelhoxy)-2-pentenal was accomplished by selective reduction of 5 to 6, followed by oxidation with pyridinium chlorochromale (59). 

What product will result from hydroboration/oxidation of 7-methylcyclo-pentene with deuterated borane, BD3 Show both the stereochemistry (spatial arrangement) and the regiochemistry (orientation) of the product. 

Hydroboration of 2-methyl-2-pentene at 25 °C followed by oxidation with alkaline H202 yields 2-methyl-3-pentanol/ but hydroboration at 160 °C followed by oxidation yields 4-methyl-l-pentanol. Suggest a mechanism. 

Amines are converted into alkenes by a two-step process called the Iiofnunn elimination. SN2 reaction of the amine with an excess of CH3I in the first stej yields an intermediate that undergoes E2 reaction when treated with silvei oxide as base. Pentylamine, for example, yields 1-pentene. Propose a structim for the intermediate, and explain why it undergoes ready elimination. 

Ytterbium, trinitratotris(dimethyl sulfoxide)-structure, 1, 97 Ytterbium, tris(acetylacetone)(4-ammo-3-penten-stereochemistry, 1,81 Ytterbium complexes acetylacetone, 2,373 dipositive oxidation state hydrated ions, 3,1109 polypyrazolylborates, 2,255 Ytterbium(III) complexes ethyl glycinate, diacetate... 

The synthesis of a series of chiral organophosphine oxide/sulfide-substituted binaphtholate ligands has recently been reported by Marks and Yu and their corresponding lanthanide complexes characterized. These complexes, generated in situ from Ln[N(TMS)2]3, cleanly catalysed enantioselective intramolecular hydroamination/cyclisation of 1-amino-2,2-dimethyl-4-pentene albeit with a low enantioselectivity of 7% ee (Scheme 10.82). 

Trimethyl- 1,3-pentanediol 2.2.4- Trimethyl-3-pentanone 2.4.4- Trimethyl- 1-pentene 2.4.4- Trimethyl-2-pentene Trimethylphosphine Trimethylphosphine oxide Trimethyl phosphate 2,3,6-Trimethylpyridine 8.6... 

A magnesium enolate of 99 is susceptible to aldol condensation with 4-pentenal, and the crude product can be directly protected to give its ethyl carbonate 100. a-Hydroxylation of the carbonyl group yields the hydroxyl carbonate 101. Reduction of the carbonyl group generates a triol, and this compound can be simultaneously converted to carbonate 102. Swern oxidation of 102 gives ketone 103, which can be rearranged25 to produce lactone product 104 (Scheme 7-32). 

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