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1.
A diastereoselective total synthesis of (±)-canadensolide is described. The key step is to introduce the α-methylene group by the ozonolysis of mono-substituted alkenes followed by reaction with a preheated mixture of CH2Br2-Et2NH. 相似文献
2.
Carbonyl compounds reacted with stable phosphonium ylides in D2O to give α-deuterated-α,β-unsaturated carbonyl compounds in the same flask. The chemical yield and deuterium incorporation are excellent under our procedure. The fragile group like ozonide was compatible with our reaction condition. 相似文献
3.
HON Yung-Son LU Ling CHANG Rong-Chi CHU Kuan-Po LIN Sheng-Wun Institute of Chemistry Academia Sinica Nankang Taipei Taiwan 《有机化学》1993,(3)
The ozonides reacted with stabilized phosphorus ylides to give the α,β-unsaturated carbonylcompounds in high yield. The Z/E ratio is dependent on the substituent of the ozonide. Their possiblemechanism was described. 相似文献
4.
In this paper we first present a 3-dimensional Lie algebra H and enlarge it into a 6-dimensional Lie algebra T with corresponding loop algebras?H and?T, respectively. By using the loop algebra?H and the Tu scheme, we obtain an integrable hierarchy from which we derive a new Darboux transformation to produce a set of exact periodic solutions. With the loop algebra?T, a new integrable-coupling hierarchy is obtained and reduced to some variable-coefficient nonlinear equations, whose Hamiltonian structure is derived by using the variational identity. Furthermore, we construct a higher-dimensional loop algebraˉH of the Lie algebra H from which a new Liouville-integrable hierarchy with 5-potential functions is produced and reduced to a complex m Kd V equation, whose 3-Hamiltonian structure can be obtained by using the trace identity. A new approach is then given for deriving multiHamiltonian structures of integrable hierarchies. Finally, we extend the loop algebra?H to obtain an integrable hierarchy with variable coefficients. 相似文献
5.
4-endo-Hydroxy-2-oxabicyclo[3.3.0]oct-7-en-3-one (9) is a useful building block in the formal total syntheses of both Types A and B furofurandione natural products. The success of Pd-catalyzed epimerization of the γ-alkenyl substituent of the bislactones makes this methodology useful and versatile. 相似文献
6.
Ozonolysis of mono-substituted alkenes A-1 followed by reacting with a preheated mixture of CH2Br2-Et2NH affords α-substituted acroleins A-2 in good yields. Under very mild reaction conditions, these α-substituted acroleins A-2 can be easily converted to α-methylene esters A-4, which could be further converted to the corresponding α-keto esters A-5. This methodology can be also applied to the preparation of α-methylene lactones B-4, α-methylene lactams, and α-keto lactones B-5 with various ring sizes. 相似文献
7.
Yung-Son Hon Tzyy-Rong HsuChun-Yan Chen Yi-Hui LinFong-Jong Chang Cheng-Han HsiehPing-Hui Szu 《Tetrahedron》2003,59(9):1509-1520
The reactivity of aryl alkyl ketone with a preheated mixture of dibromomethane and diethylamine is poor and gives an α-methylenation product in very low yield even under refluxing condition. It can be accelerated dramatically by microwave irradiation. Under microwave condition, the cyclic 1,3-dicarbonyls, aryl alkyl ketones, heteroaryl alkyl ketones and acyclic benzyl ketone give α-methylenation products in modest to good yields. 相似文献
8.
Cycloalkanones appended with an α, β-unsaturated carbonyl side chain react with 2.25 equivalents of samarium diiodide to form bicyclic or tricyclic bridgehead hydroxy compounds stereoselectively in moderate yield. 相似文献
9.
Ozonides derived from cycloalkenes reacted with 2.2 equivalents of methyl (triphenylphosphoranylidene)acetate or (triphenylphosphoranylidene)acetophenone to form trans, trans-α,β,χ-unsaturated dioates or diones, respectively. The trapping experiments have ruled out the possibility that the reaction involved the carbonyl oxide intermediate. 相似文献
10.
The aliphatic aldehydes react with catalytic amount of Dibal-H in n-pentane to give the corresponding Tishchenko products in good to excellent yields. Contrary, α-silyloxyaldehydes give α-silyloxyketones via Oppenauer oxidation under similar condition. 相似文献