Cyclopentane oxidation

The regioselectivity of epoxide-opening reactions using alkynylaluminum reagents for prostaglandin synthesis has been studied by Matthews and Eickhoff [75], With two different cyclopentane oxide derivatives, they pointed out that simple substitution of an aluminum ate complex for the usual trialkylaluminum can sometimes be useful in achieving the desired regioselectivity, as observed in Sch. 46. 

In this study, suboxides of vanadia catalysts were used in pentane, pentene, dicyclopentadiene and cyclopentane oxidation reactions. In the previous phase of the work [12,13], the role of alkali promoters on the catalyst selectivity was examined. The catalysts were reduced in situ at different temperatures and the effect of pre-reduction temperature was investigated. Controlled-atmosphere characterization of pre-reduction, post-reduction, and post-reaction catalysts were performed using X-ray diffraction. X-ray photoelectron spectroscopy, laser Raman spectroscopy and temperature-programmed desorption experiments. The objectives of this study were to determine the activity and selectivity of different suboxides of vanadia in... 

Chloro-1,2-epoxypropane (chloropropene oxide, 2-chloro-3-methyloxirane) [21947-75-1] c A-isomer [21947-76-2] frawi-isomer Cyclopentene oxide (6-oxabicyclo-[3.1.0] hexane, cyclopentane oxide, cyclopentene epoxide, 1,2-epoxycyclopentane) [285-67-6]... 

Cyclopentane oxide does not react under customary reaction conditions because of the considerable strain required to form a cyclic intermediate analogous to 64. However, on employing harsher conditions 20% of the corresponding thiiran could be obtained". 

Several procedures for making glutaric acid have been described in Organic Syntheses starting with trimethylene cyanide (28), methylene bis (malonic acid) (29), y-butyrolactone (30), and dihydropyran (31). Oxidation of cyclopentane with air at 140° and 2.7 MPa (400 psi) gives cyclopentanone and cyclopentanol, which when oxidized further with nitric acid at 65—75° gives mixtures of glutaric acid and succinic acid (32). 

Curium, oxidation number, 414 Cyclohexane, properties, 341 Cyclopentane, 340 Cyclopentene, 342... 

The hydroxylation of cyclohexane by a strain of Xanthobacterium sp. (Trickett et al. 1990). In cell extracts, a range of other substrates was oxidized including cyclopentane, pinane, and toluene (Warburton et al. 1990). 

The mechanism for the reaction catalyzed by cationic palladium complexes (Scheme 24) differs from that proposed for early transition metal complexes, as well as from that suggested for the reaction shown in Eq. 17. For this catalyst system, the alkene substrate inserts into a Pd - Si bond a rather than a Pd-H bond [63]. Hydrosilylation of methylpalladium complex 100 then provides methane and palladium silyl species 112 (Scheme 24). Complex 112 coordinates to and inserts into the least substituted olefin regioselectively and irreversibly to provide 113 after coordination of the second alkene. Insertion into the second alkene through a boat-like transition state leads to trans cyclopentane 114, and o-bond metathesis (or oxidative addition/reductive elimination) leads to the observed trans stereochemistry of product 101a with regeneration of 112 [69]. 

Palladium complexes are effective catalysts for the reductive cydization of enyne substrates [53,54], The first report of catalytic cydization of 1,6- and 1,7-enynes 115a,b to cyclopentane 116a and cyclohexane 116b derivatives appeared in 1987 (Eq. 19) [70]. The authors proposed that the Pd(II) species 117 forms by oxidative addition of acetic acid to Pd(0) (Scheme 25). Complex 117 hydrometallates the alkyne to give 118, which cyclizes to provide... 

The seminal publication [ 12] on the isolation of retigeranic acid proposed a possible biosynthetic pathway by means of cyclization from geranyl famesyl pyrophosphate (12) (Fig. 10.2) to tertiary carbocationic cyclopentane 13. A series of [1, 5] and [1, 2] hydride shifts were proposed to establish the skeletal core of the sesterterpene, whose subsequent oxidation would yield retigeranic acid. 

The synthesis of new 11-deoxyprostaglandin analogs with a cyclopentane fragment in the oo-chain, prostanoid 418, has been accomplished by a reaction sequence involving nitrile oxide generation from the nitromethyl derivative of 2-(oo-carbomethoxyhexyl)-2-cyclopenten-l-one, its 1,3-cycloaddition to cyclopenten-l-one and reductive transformations of these cycloadducts (459). Diastereoisomers of a new prostanoid precursor 419 with a 4,5,6,6a-tetrahydro-3aH-cyclopent[d isoxazole fragment in the oo-chain have been synthesized. Reduction of 419 gives novel 11-deoxyprostanoids with modified a- and oo-chains (460). 

The [4+ 4]-homolog of the [4 + 2]-Alder-ene reaction (Equation (48)) is thermally forbidden. However, in the presence of iron(m) 2,4-pentanedioate (Fe(acac)3) and 2,2 -bipyridine (bipy) ligand, Takacs57 found that triene 77 cyclizes to form cyclopentane 78 (Equation (49)), constituting an unprecedented formal [4 + 4]-ene cycloisomerization. The proposed mechanism for this transformation involves oxidative cyclization followed by /3-hydride elimination and reductive elimination to yield the cyclized product (Scheme 18). 

Dipolar addition is closely related to the Diels-Alder reaction, but allows the formation of five-membered adducts, including cyclopentane derivatives. Like Diels-Alder reactions, 1,3-dipolar cycloaddition involves [4+2] concerted reaction of a 1,3-dipolar species (the An component and a dipolar In component). Very often, condensation of chiral acrylates with nitrile oxides or nitrones gives only modest diastereoselectivity.82 1,3-Dipolar cycloaddition between nitrones and alkenes is most useful and convenient for the preparation of iso-xazolidine derivatives, which can then be readily converted to 1,3-amino alcohol equivalents under mild conditions.83 The low selectivity of the 1,3-dipolar reaction can be overcome to some extent by introducing a chiral auxiliary to the substrate. As shown in Scheme 5-51, the reaction of 169 with acryloyl chloride connects the chiral sultam to the acrylic acid substrate, and subsequent cycloaddition yields product 170 with a diastereoselectivity of 90 10.84... 

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