Yaşar Sütbeyaz

A new and stereospecific synthesis of conduritol-F and conduritol-Bs

Abstract A new and stereospecific synthesis for conduritol-F has been developed starting from transbenzenediacetate 5 and oxepine-benzeneoxide 8 where the oxygen functionalities were introduced in both cases by photooxygenation; suitable ring opening reactions gave the desired conduritol-F. Acid-catalyzed ring opening reaction of 11 in aceticanhydride gave conduritol-F and conduritol-B in a ratio of 2:1.

CoTPP-catalyzed rearrangement of 1.4-endoperoxides

Abstract Bicyclic endoperoxides with strained and perturbed diene moiety have been submitted to CoTPP-catalyzed rearrangement. Side reaction, like formation of epoxyenone, has been suppressed and yield of the formation of bisepoxides highly increased.

CoTPP-catalyzed reaction mechanism of the cycloheptatriene 1.4-endoperoxide

Abstract CoTPP-catalyzed reaction mechanism of the cycloheptatriene 1.4-endoperoxide is studied. Beside the expected bisepoxide, two isomeric open-chain aldehydes are isolated. The mechanism for the formation of the aldehydes are discussed in terms of radical intermediates.

Synthesis of haloconduritols from an endo-cycloadduct of furan and vinylene carbonate

Abstract A method for preparing haloconduritols having a conduritol-A construction is described. A mixture of endo- and exo-cycloadduct derivatives prepared from the Diels–Alder reaction of furan and vinylene carbonate was converted into diacetate derivatives by hydrolysis (K2CO3/MeOH) followed by acetylation (Ac2O/pyridine). Boron trihalide (BBr3 or BCl3)-assisted ring-opening of the endo-diacetate in CH2Cl2 at −78°C gave (1α,2α,3β,6β)-6-halogeno-4-cyclohexene-1,2,3-triol 1,2-diacetate from which the corresponding triacetate was prepared by acetylation (AcCl). trans-Esterification of the triacetate (MeOH/HCl) afforded (1α,2α,3β,6β)-6-halogeno-4-cyclohexene-1,2,3-triol (X=Br or Cl). BF3-Assisted ring-opening of the endo-diacetate in CH2Cl2 gave (1α,2α,3β,6β)-6-chloro-4-cyclohexene-1,2,3-triol 1,2-diacetate by means of halogen exchange.

A novel and stereospecific synthesis of conduritol-A

A new and stereospecific synthesis for conduritol-A has been developed starting from cyclohexa-1,4-diene where hydroxy groups have been introduced by classical KMnO4-oxidation followed by photo-oxygenation; suitable ring-opening reactions gave the desired conduritol-A.

Heterogenous Oxidation of [2.2.1] Bridged Bicyclic Alkenes with KMnO4-CuSO4.5H2O: An Alternative Ozonolysis

Abstract Seven [2.2.1] bridged alkenes were cleaved to the corresponding dialdehyde products by neutral heterogenous oxidation with KMnO4-CuSO4.5H2O. While endo, endo-dimethyl bicyclo[2.2.2]oct-5-ene-2,3-dicarboxylate, [2.2.2] bridged alkene, gave the corresponding α-hydroxy ketone, endo, endo-dimethyl bicyclo[3.2.2]non-8-ene-6,7-dicarboxylate afforded a diketone product.

A Novel Synthesis of Conduritol-C and Conduritol-E via p-Benzoquinone

Abstract A new and stereospecific synthesis for Conduritol-C 8 and Conduritol-E 13a has been developed starting from p-benzoquinone 1. 1,4-oxygen functionalities were introduced in both synthesis by the reduction of dibromo p-benzoquinone 2 with NaBH4. 2,3-oxygen functionalities were introduced by KMnO4 oxidation of 4 for Conduritol C 8. Oxidation of 3 with m-chloroperbenzoic acid gave 9. Acid-catalyzed ring opening reaction of 9 gave 10a which leads to Conduritol-E.

A Novel Synthesis of DL-proto-, and DL-vibo-Quercitol via 1, 4-Cyclohexadiene

Abstract Photooxygenation of 1, 4-cyclohexadiene 3 followed by reduction with LiAlH4 or thiourea gave (25/1)-cyclohex-3-ene-triol 7a. trans-Hydroxylation of triol 7a with three different methods afforded both of proto-quercitol la and vibo-quercitol 2a.

Evidence for the formation of a new five-membered ring cyclic allene: Generation of 1-cyclopenta-1,2-dien-1-ylbenzene

Treatment of 1-(2-iodocyclopent-1-en-1-yl)benzene (13), dissolved in benzene, with potassium t-butoxide resulted in the formation of 1-(2-phenylcyclopent-1-en-1-yl)benzene (15) and 1-cyclopent-1-en-1-ylbenzene (5) in a ratio of 1:1.

One-pot synthesis from 1,4-cyclohexadiene of (±)-1,4/2,5-cyclohexanetetrol, a naturally occurring cyclitol derivative

Abstract SeO 2 -catalyzed direct hydroxylation of 1,4-cyclohexadiene with two molar equivalents of 30% H 2 O 2 afforded (±)-1,4/2,5-cyclohexanetetrol, a naturally occurring cyclitol derivative, as the sole product in a good yield (88%).