- Exaltone (=Cyclopentadecanone) from Isomuscone (=Cyclohexadecanone), a one-C-atom ring-contraction methodology via a stereospecific favorskii rearrangement: Regioselective application to (-)-(R)-muscone
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Treatment of cyclohexadecanone (1g; with I2 (2.2 mol-euqiv.) and KOH in MeOH) furnished the unsaturated (Z)-ester 2g in 83% yield, via a stereospecific Favorskii rearrangement (Scheme 1). Further treatment with 3-chloroperbenzoic acid (m-CPBA) afforded the unreported epoxy ester 3g (88% yield), which was cleaved in 33% yield to Exaltone (=cyclopentadecanone; 1f) with NaOH in MeOH/H2O and then HCl at 65°. This methodology was similarly extended to higher (C17) and lower (C15 to C11) cyclic ketone analogues, as well as regioselectively to (-)-(R)-muscone (5c) and homomuscone (5f) (Scheme 2). Olfactive properties of the corresponding macrocyclic 1-oxaspiro[2,n]alkanes and -alkenes 4 and 8, resulting from a Coreyi-Chaykovsky oxiranylation, are also presented. Copyright
- Chapuis, Christian,Robvieux, Fabrice,Cantatore, Carole,Saint-Leger, Christine,Maggi, Laurent
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p. 428 - 447
(2012/05/07)
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- Structure-reactivity relationship for alcohol oxidations via hydride transfer to a carbocationic oxidizing agent
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Second-order rate constants were determined for the oxidation of 27 alcohols (R1R2CHOH) by a carbocationic oxidizing agent, 9-phenylxanthylium ion, in acetontrile at 60°C. Alcohols include open-chain alkyl, cycloalkyl, and unsaturated alcohols. Kinetic isotope effects for the reaction of 1-phenylethanol were determined at three H/D positions of the alcohol (KIEα-D=3.9, KIEβ-D3=1.03, KIE OD=1.10). These KIE results are consistent with those we previously reported for the 2-propanol reaction, suggesting that these reactions follow a hydride-proton sequential transfer mechanism that involves a rate-limiting formation of the α-hydroxy carbocation intermediate. Structure-reactivity relationship for alcohol oxidations was deeply discussed on the basis of the observed structural effects on the formation of the carbocationic transition state (Cδ+-OH). Efficiencies of alcohol oxidations are largely dependent upon the alcohol structures. Steric hindrance effect and ring strain relief effect win over the electronic effect in determining the rates of the oxidations of open-chain alkyl and cycloalkyl alcohols. Unhindered secondary alkyl alcohols would be selectively oxidized in the presence of primary and hindered secondary alkyl alcohols. Strained C7-C11 cycloalkyl alcohols react faster than cyclohexyl alcohol, whereas the strained C5 and C12 alcohols react slower. Aromatic alcohols would be efficiently and selectively oxidized in the presence of aliphatic alcohols of comparable steric requirements. This structure-reactivity relationship for alcohol oxidations via hydride-transfer mechanism is hoped to provide a useful guidance for the selective oxidation of certain alcohol functional groups in organic synthesis. Copyright
- Lu, Yun,Bradshaw, Joshua,Zhao, Yu,Kuester, William,Kabotso, Daniel
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p. 1172 - 1178
(2013/01/12)
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- Gene encoding cyclododecanone monooxygenase
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The invention relates to a new strain of Pseudomonas putida (designated as HI-70) and to the isolation, cloning, and sequencing of a cyclododecanone monooxygenase-encoding gene (named cdnB) from said strain. The invention also relates to a new cyclododecanone monooxygenase and to a method of use of the cyclododecanone monooxygenase-encoding gene.
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- Diradical-promoted (n + 2 - 1) ring expansion: An efficient reaction for the synthesis of macrocyclic ketones
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(Chemical Equation Presented) A diradical-promoted (n + 2 - 1) ring expansion reaction based on vinyl side chain insertion (+2C) and decarbonylation (-1C) has been developed. Flash vacuum pyrolysis (FVP) of medium- and large-ring 2-trimethylsilyloxy-2-vinyl-cycloalkanones at 500-600°C affords the one-carbon ring-expanded cycloalkanones in good yields. Methyl groups on the vinyl moiety are transformed regiospecifically as corresponding α- and β-substituents, respectively. 2-Ethynyl precursor analogues react in a manner similar to give α,β-unsaturated cyclic ketones.
- Rueedi, Georg,Oberli, Matthias A.,Nagel, Matthias,Hansen, Hans-Jurgen
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p. 3179 - 3181
(2007/10/03)
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- The effect of pressure on cyclizations. The ring-size dependent reaction volumes of the cyclization of 1-alkenes to cycloalkanes. Experimental measurement of activation and reaction volumes of the intramolecular diels - Alder reaction of 1,3,8-nonatriene and 1,3,9-decatriene. Temperature dependence of activation and reaction volumes
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The volumes of reaction determined for the hypothetical cyclization of 1-alkenes to cycloalkanes decrease continUOusly from the formation of cyclopropane (ΔV(R) = -5.5 cm3 mol-1) up to the formation of cyclodecane (ΔV(R) = -32.3 cm3 mol-1) and seem to be constant for the larger rings. The analysis of the packing coefficients (η = V(w)/V) leads to the conclusion that this ring-size dependent decrease in volume results from the different packing of cyclic and acyclic compounds rather than from the changes in their intrinsic molecular volumes. The investigation of the intramolecular Diels-Alder reactions of (E)-l,3,8-nonatriene (E)-1 and (E)- 1,3,9-decatriene (E)-2 leading to the bicyclo[4.3.0]nonenes cis- and trans-4 (ΔV≠/ΔV(R) [cm3 mol-1] -24.8/-32.0 and -24.8/-28.5, respectively) or bicyclo[4.4.0]decenes cis- and trans-6 (-37.6/-45.4 and -35.0/-37.4, respectively) confirms the ring-size dependence of the activation and reaction volumes. The dependence of the effect of pressure from the number of newly forming rings is illustrated with the thermolysis of (Z)-1,3,8- nonatriene (Z)-1 in which an intramolecular Diels-Alder reaction leading to bicyclo [4.3.0]nonene cis-4 competes with a sigmatropic [1,5] hydrogen shift leading to (E,Z)-1,5,7-nonatriene 7. The use of high pressure causes a reversal of selectivity.
- Diedrich, Matthias K.,Kl?rner, Frank-Gerrit
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p. 6212 - 6218
(2007/10/03)
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- Photoinduced Molecular Transformations. Part 155. General Synthesis of Macrocyclic Ketones based on a Ring Expansion involving a Selective β-Scission of Alkoxyl Radicals, its Applications to a New Synthesis of (+/-)-Isocaryophyllene and (+/-)-Caryophyllene, and a Conformational Analy...
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The method used for a general synthesis of macrocyclic ketones based on a ring expansion involving a selective β-scission of alkoxyl radicals devised by Suginome and Yamada was extended and modified.Thus, cycloalkanones were transformed into the corresponding α-(ω-iodoalkyl)-cycloalkanones by alkylation of the corresponding lithium enolates with either 1,3-diiodopropane or 1,4-diiodobutane.Treatment of these α-iodoalkyl cyclic ketones with samarium iodide gave bicyclic tertiary alcohols.The generation of the alkoxyl radicals from the bicyclic alcohols by irradiation of the corresponding hypoiodites generated with mercury(II) oxide - iodine - pyridine in benzene resulted in a selective β-scission of their ring-junction bond to give high yields of macrocyclic ketones carrying an iodine which can be removed with tributyltin hydride.The method was then applied to new syntheses of (+/-)-isocaryophyllene and (+/-)-caryophyllene.Thus, ω-iodopropylation of ethyl 7,7-dimethyl-2-oxobicyclooctane-3-carboxylate, followed by cyclization of the resulting α-(ω-iodoalkyl)cycloalkanone with samarium diiodide, gave cis-transoid-cis-ethyl 1-hydroxy-4,4-dimethyltricyclo2,5>undecane-8-carboxylate (69percent).The ethoxycarbonyl group of this tricyclic alcohol was transformed into a methyl group by the standard method.Irradiation of a solution of the hypoiodite, prepared by the method mentioned above, with Pyrex-filtered light gave the corresponding cis-bicycloundecenone (15percent), its exomethylene isomer (2,5>undecan-1-ol mentioned above were correlated with the three products.
- Suginome, Hiroshi,Kondoh, Takahiko,Gogonea, Camelia,Singh, Vishwakarma,Goto, Hitoshi,Osawa, Eiji
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- Ring Enlargement of Boracyclanes via Sequential One-Carbon Homologation. The First Synthesis of Boracyclanes in the Strained Medium Ring Range.
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We explored the Matteson homologation procedure as a means of enlarging the size of the ring in B-methoxyboracyclanes.
- Brown, Herbert C.,Phadke, Avinash S.,Rangaishenvi, Milind V.
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p. 6263 - 6264
(2007/10/02)
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- OXIDATION OF ALCOHOLS USING DIMETHYL SULFOXIDE AND TRICHLORMETHYL CHLOROFORMATE
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Treatment of structurally diverse alcohols with dimethyl sulfoxide in the presence of trichloromethyl chloroformate (phosgene dimer) and triethylamine efficiently afforded the corresponding aldehydes or ketones in excellent yields.
- Takano, Seiichi,Inomata, Kohei,Tomita, Shun'ichi,Yanase, Masashi,Samizu, Kyiohiro,Ogasawara, Kunio
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p. 6619 - 6620
(2007/10/02)
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- Oxidation of Secondary Alcohols with t-Butyl Hypochlorite in the Presence of Pyridine
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When treated with t-butyl hypochlorite and pyridine in methylene dichloride, secondary alcohols give the corresponding ketones in very high yield.The relative reactivities of a number of p-substituted 1-phenylethanols containing electron-donating and -withdrawing substituents were investigated.Oxidation of cis- and trans-4-t-butylcyclohexanol, as well as some other cycloalkanols, proceeds with the same relative rate.On the basis of this and other data a cyclic transition state and loss of α-hydrogen of the starting alcohols as hydride ion are proposed as characteristics of the reaction mechanism.
- Milovanovic, Jovan N.,Vasojevic, Miorad,Gojkovic, Svetislav
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p. 533 - 536
(2007/10/02)
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- A Catalytic Model for the Dioldehydratase Reaction
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The diastereoisomeric 6,7-dihydroxycycloundecyl iodides (3a), (3b), and (3c) have been synthesised; their conversion into cycloundecanone (12) in the presence of sodium borohydride and traces of cobalt complexes provides the first catalytic model for the coenzyme B12 catalysed dioldehydratase reaction.
- Mueller, Peter,Retey, Janos
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p. 1342 - 1344
(2007/10/02)
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- Medium-ring Ketone Synthesis. Synthesis of Eight- to Twelve-membered Cyclic Ketones based on the Intramolecular Cyclization of Large-Membered Lactam Sulfoxides or Sulfones
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An effective general method for the construction of medium-ring ketones from the corresponding ω-bromocarboxylic acids is described.When the diamide disulfide 10 was treated with NaBH4 and NaH in 2-propanol, reductive cleavage of the sulfur-sulfur bond and concomitant intramolecular coupling of the resulting thiolate anion with the terminal bromide took place and the large-ring lactam sulfide 7, which was the key intermediate for the synthesis of medium-ring ketones, was obtained.Although lithium diisopropyl amide (LDA) treatment of 11 followed by reductive desulfurization provided cycloundecanone (13d) in only 19.5percent yield, intramolecular cyclization of the α-methylated analogues 17 with LDA proceeded smoothly and the keto sulfoxides 18 were obtained in quantitative yields.In the case of the lactam sulfones 21, tert-BuOK was effective as a base for the intramolecular cyclization, affording the keto sulfones 22 in quantitative yields.The keto sulfoxides 18 and sulfones 22 were subjected to reductive desulfurization with Al-Hg to yield medium-ring ketones 19 and 13, respectively, in high yields.Keywords - medium-ring ketone; intramolecular cyclization; large-ring lactam sulfide; bis(2-methylaminophenyl) disulfide; 2-methylaminobenzenethiol; reductive desulfurization; sulfur-stabilized carbanion; active methylene
- Ohtsuka, Yasuo,Oishi, Takeshi
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p. 454 - 465
(2007/10/02)
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- 186. Steric Effects on Reaction Rates. Rate and Equilibrium Constants for Oxidation of Cyclanols
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Equilibrium constants for oxidations of cyclanols by cyclohexanone in benzene have been determined in the presence of aluminium isopropoxide.The free energies of the equilibrium (ΔGox) are correlated with equilibrium constants for dissociation of cyanohydrins, rate constants for cyclanol oxidation with chromic acid, ketone reduction with sodium borohydride and trifluoroethanolysis of tosylates.
- Paul, Mueller,Blanc, Jacky
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p. 1759 - 1766
(2007/10/02)
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