34310-95-7Relevant academic research and scientific papers
Chemo- and diastereoselectivities in the oxidation of cyclopentenols with dimethyldioxirane and methyl(trifluoromethyl)dioxirane
D'Accolti, Lucia,Fiorentino, Michele,Fusco, Caterina,Rosa, Angela M.,Curci, Ruggero
, p. 8023 - 8027 (1999)
A comparison of the diastereoselectivity and the chemoselectivity (epoxidation versus allylic oxidation) attained in the oxidation of cyclopentenols using dimethyldioxirane and methyl(trifluoromethyl)dioxirane is reported. The results indicate that with both dioxiranes diastereoselective epoxidation of allylic cyclopentenols is accompanied by competitive allylic oxidation to the corresponding enone; for the latter a likely rationale is proposed.
Eu(OTf)3-Catalyzed highly regioselective nucleophilic ring opening of 2,3-epoxy alcohols: An efficient entry to 3-substituted 1,2-diol derivatives
Uesugi, Shun-Ichiro,Watanabe, Tsubasa,Imaizumi, Takamichi,Shibuya, Masatoshi,Kanoh, Naoki,Iwabuchi, Yoshiharu
supporting information, p. 4408 - 4411 (2015/01/16)
In our study of the total synthesis of (+)-irciniastatin A, we found a need to develop a method that enables a C3-selective nucleophilic ring opening of 2,3-epoxy alcohol by MeOH, by which we found that the use of combined catalytic amounts of Eu(OTf)3 and 2,6-di-tert-butyl-4-methylpyridine (DTBMP) enables the intended transformation to obtain 3-methoxy-1,2-diol efficiently. Promising features of a protocol that effects a highly regioselective nucleophilic ring opening of 2,3- and 3,4-epoxy alcohols using various nucleophiles including alcohols, thiols, and unprotected amines are described.
A highly chemoselective, diastereoselective, and regioselective epoxidation of chiral allylic alcohols with hydrogen peroxide, catalyzed by sandwich-type polyoxometalates: Enhancement of reactivity and control of selectivity by the hydroxy group through metal-alcoholate bonding
Adam, Waldemar,Alsters, Paul L.,Neumann, Ronny,Saha-Moeller, Chantu R.,Sloboda-Rozner, Dorit,Zhang, Rui
, p. 1721 - 1728 (2007/10/03)
Sandwich-type polyoxometalates (POMs), namely [VZnM2(ZnW9O34)2]q- [M = Mn(II), Ru(III), Fe(III), Pd(II), Pt(II), Zn(II); q = 10-12], are shown to catalyze selectively the epoxidation of chiral allylic alcohols with 30% hydrogen peroxide under mild conditions (ca. 20 °C) in an aqueous/organic biphasic system. The transition metals M in the central ring of polyoxometalate do not affect the reactivity, chemoselectivity, or stereoselectivity of the allylic alcohol epoxidation by hydrogen peroxide. Similar selectivities, albeit in significantly lower product yields, are observed for the lacunary Keggin POM [PW11O39]7-, in which a peroxotungstate complex has been shown to be the active oxidizing species. All these features support a tungsten peroxo complex rather than a high-valent transition-metal oxo species operates as the key intermediate in the sandwich-type POM-catalyzed epoxidations. On capping of the hydroxy functionality through acetylation or methylation, no reactivity of these hydroxy-protected substrates [1a(Ac) and 1a(Me)] is observed by these POMs. A template is proposed to account for the marked enhancement of reactivity and selectivity, in which the allylic alcohol is ligated through metal - alcoholate bonding, and the H2O2 oxygen source is activated in the form of a peroxotungsten complex. 1,3-Allylic strain promotes a high preference for the threo diastereomer and 1,2-allylic strain a high preference for the erythro diastereomer, whereas tungsten - alcoholate bonding furnishes high regioselectivity for the epoxidation of the allylic double bond. The estimated dihedral angle α of 50 - 70° for the metal - alcoholate-bonded template of the POM/H2O2 system provides the best compromise between 1,2A and 1,3A strain during the oxygen transfer. In contrast to acyclic allylic alcohols 1, the M-POM-catalyzed oxidation of the cyclic allylic alcohols 4 by H2O2 gives significant amounts of enone.
Steric and electronic effects in the diastereoselective catalytic epoxidation of cyclic allylic alcohols with methyltrioxorhenium (MTO)
Adam, Waldemar,Mitchell, Catherine M.,Saha-Moeller, Chantu R.
, p. 785 - 790 (2007/10/03)
The steric effects of allylic substituents in the epoxidations with methyltrioxorhenium/urea/hydrogen peroxide adduct (MTO/UHP) have been assessed for a series of 3-alkyl-substituted cyclohexenes. The trans selectivity increases with the size of the substituent and the diastereoselectivities follow an excellent linear correlation with the steric substituent constants of Taft (E(s)) or Charton (v). Good cis selectivity is observed in the epoxidation of the cyclic allylic alcohols 2-cyclopentenol and 2-cyclohexenol due to a hydroxy-directing effect through hydrogen bonding; however, for 2-cycloheptenol and 2-cyclooctenol hydrogen bonding is ineffective and steric interactions cause a higher trans selectivity. The conformationally fixed cis- and trans-5-tert-butyl-2-cyclohexenols serve as suitable substrates for gauging the dihedral angle of the transition states for the oxygen transfer in these epoxidations. Thus, the MTO/UHP oxidant favours a quasi-equatorial arrangement of the hydroxy group for effective hydrogen bonding (hydroxy-group directivity), in analogy to m- chloroperbenzoic acid (m-CPBA) and dimethyldioxirane (DMD), and a dihedral angle of ca. 130°is suggested.
Synthesis of C-5'-nor-dideoxycarbanucleosides structurally related to neplanocin C
Comin, Maria J.,Pujol, Carlos A.,Damonte, Elsa B.,Rodriguez, Juan B.
, p. 2219 - 2231 (2007/10/03)
Purine carbanucleosides built on a 6-oxabicyclo[3.1.0]hexane template were synthesized from readily available 2-cyclopentenone employing a Mitsunobu reaction to incorporate the base onto the carbocyclic ring. Both adenosine and guanosine analogues exhibited moderate antiviral activity.
Regiochemical Control of the Ring-Opening of Epoxides by Means of Chelating Processes, 13. Synthesis and Ring-Opening Reactions of the Diastereoisomeric cis- and trans-Epoxides Derived from 3-(Benzyloxy)cyclopentene and 2-(Benzyloxy)-2,5-dihydrofuran
Crotti, Paolo,Bussolo, Valeria Di,Favero, Lucilla,Macchia, Franco,Pineschi, Mauro
, p. 1675 - 1686 (2007/10/03)
The regiochemical outcome of the ring-opening of epoxides bearing remote polar functionalities has been established in the case of carbocyclic (1 and 2) and the corresponding furanosidic (3 and 4) title epoxides. Under standard conditions, the regioisomeric C-1 products are the sole (from trans epoxides 2 and 4) or predominant (from cis epoxides 1 and 3) ring-opening products. However, under chelating conditions, and only in the case of the cis epoxides 1 and 3, a consistent increase in C-2 selectivity is unexpectedly observed. - Keywords: Epoxides; Regioselectivity; Nucleophilic additions; Synthetic methods
Hydroxy-assisted Chemo- and Stereo-selective Epoxidation Catalysed by a Titanium Silicate Molecular Sieve (TS-1)/H2O2 System
Kumar, Rajiv,Pais, Godwin C. G.,Pandey, Bipin,Kumar, Pradeep
, p. 1315 - 1316 (2007/10/02)
The TS-1/H2O2 system efficiently catalyses the hydroxy-assisted chemoselective epoxidation of α-hydroxyalkene in geraniol, and the stereoselective epoxidation of cyclopent-2-en-1-ol/cyclohex-2-en-1-ol producing the epoxide which is cis to OH with high selectivity (90:10 cis:trans).
Novel Synthesis of syn-α,β-Epoxy Alcohols by Diastereoselective Carbonyl Reduction of α,β-Epoxy Ketones
Kawakami, Takayo,Shibata, Ikuya,Baba, Akio,Matsuda, Haruo,Sonoda, Noboru
, p. 8625 - 8626 (2007/10/02)
A novel tin hydride reagent, Bu3SnH-Bu4NCN, reduced α,β-epoxy ketones to the corresponding syn-α,β-epoxy alcohols in high diastereoselectivities.
Asymmetric Catalysis by Vitamin B12. The Mechanism of the Cob(I)alamin-Catalyzed Isomerization of 1,2-Epoxycyclopentane to (R)-Cyclopent-2-enol
Bonhote, Pierre,Scheffold, Rolf
, p. 1425 - 1444 (2007/10/02)
The isomerization of 1,2-epoxycyclopentane (1) to enantiomerically enriched (R)-cyclopent-2-enol (2) in protic solvents is catalyzed by cob(I)alamin.The enantiomeric excess (e.e.) of (R)-2 is usually ca. 60percent; it is only slightly dependent on the temperature, but increases with decreasing dielectric constant ε of the solvent.Standard kinetic methods show the reaction to be first order in vitamine B12 and zero order in 1.The rate constant increases exponentially with increasing ε of the solvent.An Arrhenius plot at ε = 40 gives activation parameters ΔH(excit.) = 78 +/- 4 kJ*mol-1 and ΔS(excit.) = -49 +/- 1 J*mol-1*K-1.The isomerization 1 --> 2 proceeds in two steps (Schemes 2 and 7): i) The epoxide ring is first opened by the proton-assisted fast and irreversible nucleophile attack of the chiral CoI catalyst to form diastereomeric (1R,2R)- and (1S,2S)-(2-hydroxycyclopentyl)cob(III)alamins 6 in a ratio of ca. 4:1 which are the dominant species in the steady state; ii) The intermediates 6 then decompose in the rate limiting step to form 2 and recycled catalyst.Experiments with specifically 2H-labeled 1 showed the hydro-cobalt elimination 6 --> 2 to be non-stereoselective.It proceeds via reversible Co-C bond homolysis to a free 2-hydroxycyclopentyl radical from which stereoelectronically controlled H-abstraction by CoII takes place.
Stereospecific Syntheses of the Four Diastereomeric 2-Amino-5-phenoxycyclopentanols
McCarthy, James R.,Wiedeman, Paul E.,Shuster, Albert J.,Whitten , Jeffrey P.,Barbuch, Robert J.,Huffman, John C
, p. 3095 - 3103 (2007/10/02)
Stereospecific synthetic routes are described for the formation of the three contiguous chiral centers in the four diastereomeric 2-amino-5-phenoxycyclopentanols 1a-4a.All four stereoisomers (1a-4a) were prepared, starting from 3-chlorocyclopentene (6).Am
