The Baeyer-Villiger reaction is an oxidative transformation of katones into esters by peracid,which is an important method for functional group transformation as well as for ring expansion in organic synthesis.Oxidation of cyclic ketones into lactones has been employed for heterocycles and functionalized carbon chains.The reaction is reliable for controlling the regioselectivity and stereochemistry of the products,it is widely used as a key ring expansion step for the synthesis of natural products,including antibiotics steroids and pheromones.Particularly many complex structure of oxyacids would be synthesized by lactones via hydrolysis.In this paper we reported that（+）-chrysanthenone（2）(\20D=+38.0) was obtained from crude（+）-verbenone without purification on the irradiation with ultraviolet light in Quartz flask.When（+）-chrysanthenone underwent Baeyer-Villiger oxidation by using oxidant H2O2and CH3COOH as the oxidant the lactone 2,8,8-trimethyl-6-oxo-7-oxabicyclo[3.2.1]oct-2-ene（3）(\20D=+65.0) was formed.Then compound 3 was hydrolysized to afford 2,2,4-trimethyl-5-hydroxycyclohexen-3-yl carboxylic acid（4）(\20D=+50.0).Compound 4 was oxidized by pyridinium chlorochromate to afford conjugated ketone acid 2,2,4-trimethy-3-oxocyclohexen-4-yl carboxylic acid 5.The structure of compounds 2,3,4,5 were identified by（）1H NMR,IR and chemical reaction.The mechanism of oxidation of lactone 3 in the Baeyer-Villiger reaction was discussed.In this reaction the migrating group is a secondary carbon group holding allyl function.
Two novel compounds（4a and 4b） were obtained by the association of 2,2,4-trimethyl-3-hydroxy-5-cyclohexenecarboxylate with （S） -isoserine derivatives. The space location of the hydroxyl group of compound 1 was identified via the formation of lactone 6. Fe2 （SO4）3·xH2O was used as the catalyst for the synthesis of lactone 6. The carboxyl group was selectively protected with diazomethane. All the products were characterized via ^1H NMR and mass spectra. The Docking study showed that the associations have the potential therapeutic use of DPP-Ⅳ inhibitor.
WANG LeiZHENG Qing-chuanSONG Zhi-guangFANG Wei-shuoLI Ye-zhiHUANG Hua-min
We reported a facile synthesis of (-)-isochrysanthenone(2) from (-)-α-pinene in a high yield. When (-)-α-pinene reacted with O 2 in the presence of Co[4-Me(C 5H 4N) 2]Br 2 used as a catalyst, the crude product of (-)-verbenone(1) was formed, and the crude product 1 was directly irradiated with ultraviolet light and converted into the (-)-isochrysanthenone(2). The structure of compound 2 was converted to a cyclic ester(4) by Baeyer-Villiger oxidation, the compound 4 was hydrolyzed to form a crystal 2,2,4-trimethyl-5-oxy-3-cyclohexenyl carboxylic acid 5. Compound 5 was confirmed by IR, 1H NMR and X-ray crystal analysis. In summary, we found that under the condition of photochemical rearrangement of (-)-verbenone and (+)-verbenone, different compounds were obtained, they are not enantiomers.
Synthetic Aperture Radar(SAR) imaging systems have been widely used in civil and military fields due to their all-weather and all-day abilities and various other advantages. However, due to image data exponentially increasing, there is a need for novel automatic target detection and recognition technologies. In recent years, the visual attention mechanism in the visual system has helped humans effectively deal with complex visual signals. In particular, biologically inspired top-down attention models have garnered much attention recently. This paper presents a visual attention model for SAR target detection, comprising a bottom-up stage and top-down process.In the bottom-up step, the Itti model is improved based on the difference between SAR and optical images. The top-down step fully utilizes prior information to further detect targets. Extensive detection experiments carried out on the benchmark Moving and Stationary Target Acquisition and Recognition(MSTAR) dataset show that, compared with typical visual models and other popular detection methods, our model has increased ability and robustness for SAR target detection, under a range of Signal to Clutter Ratio(SCR) conditions and scenes. In addition, results obtained using only the bottom-up stage are inferior to those of the proposed method, further demonstrating the effectiveness and rationality of a top-down strategy. In summary, our proposed visual attention method can be considered a potential benchmark resource for the SAR research community.
It is one of the most attractive types of asymmetric synthesis that chiral commpounts are generated under the influence of chiral catalysts. In recent years catalytic asymmetric Michael addition by chiral metal complexes has been recognized as an efficient method for obtaining asymmetric products. In this work we reported that using potassium thiazolidine -2-thione-4-carboxylate [(R)-TTCA·K] as the chiral catalyst, the addition reaction of cyclohexanone with acrylonitrile was carried out and optically active (S)-(+)-2-cyanoethyl cyclohexanone 1 ([α] 20 D=+2.8°, e.e. 19%) and hydrolysis product of 1, (S)-(-)-2-oxocyclohexanepropionic acid 2 ([α] 20 D=-2.95°, e.e. 19%), were obtained. Enantiomeric excess of compound 1 was determined by resolution of (R,S)-2-oxocyclohexanepropionic acid with (-)-quinine. Compounds 1 and 2 were easily racemized at a long time for laying aside and in the presence of dil H 2SO 4 or dil base. When (S)-(+)-2-cyanoethyl cyclohexanone reacts with ethylene glycol in the presence of toluene sulfonic acid as the catalyst the racemic 2-ethylendioxy cyclohexyl propionitrile was obtained. The mechanism of the reaction of cyclohexanone with acrylonitrile would be a complicated catalysis process.
