共查询到20条相似文献,搜索用时 15 毫秒
1.
A concise synthesis of tetrabenazine and dihydrotetrabenazine is described. The key feature of this synthesis is the intramolecular aza-Prins-type cyclization of an amino allylsilane via oxidative C-H activation. 相似文献
2.
A novel Pd-catalyzed Wacker-type oxidative cyclization under air is described. By using this cyclization, a series of 2-methylquinolines are readily prepared with good yields under mild conditions. 相似文献
3.
Hai-Qing Luo 《Tetrahedron letters》2010,51(7):1041-5082
A highly efficient method for the synthesis of fluorinated 2,6-trans dihydropyrans via BF3·Et2O-promoted Prins cyclization of allenic alcohols and aldehydes is developed. Various 2,6-trans fluorodihydropyrans are obtained in moderate to good yields with excellent diastereoselectivities. 相似文献
4.
A rapid enantiospecific stereoselective synthesis of the 6,6,5-ring system of the novel tricyclic elisabethin diterpenes, starting from (R)-carvone, employing a ROM-RCM sequence as the key step, has been accomplished. 相似文献
5.
[reaction: see text] The synthesis of allocyathin B(3) from an advanced intermediate possessing the ring system and relative stereochemistry but lacking the isopropyl and hydroxymethyl groups is reported. The isopropyl group was introduced by radical cyclization of a methyl propargyl acetal of an alpha-bromo ketone, and the hydroxymethyl group was generated by Pd-catalyzed carbonylation of a vinyl triflate. The route provides functionalized intermediates that could allow access to more complex members of the cyathin family of diterpenes. 相似文献
6.
7.
[reaction: see text] The hexahydropyrrolo[2,3-b]indoline skeleton is readily accessed by the zinc triflate-mediated alkylation of tryptamine derivatives. The methodology was employed in a three-step total synthesis of debromoflustramine B. 相似文献
8.
An approach to the synthesis of hamigeran B is described. Key steps include a Tius-Nazarov cyclization and a palladium-catalyzed oxidative cyclization of an α-hydroxyenone. 相似文献
9.
Caussanel F Wang K Ramachandran SA Deslongchamps P 《The Journal of organic chemistry》2006,71(19):7370-7377
Total syntheses of two new (+/-)-kempane derivatives 30 and 47 were achieved with transannular Diels-Alder reaction (TADA) serving as the key step for the stereoselective formation of tricyclic [6.6.5] system 3. This synthetic approach also reveals that the geometry of the C3 group of such a tricyclic system plays an important role for the formation of the seven-membered kempane skeleton. 相似文献
10.
11.
12.
Jung JC Lim E Lee Y Min D Ricci J Park OS Jung M 《Molecules (Basel, Switzerland)》2012,17(2):2091-2102
The total synthesis and structure determination of cis- and trans-flocoumafen was described. The key synthetic steps involve Knoevenagel condensation with p-methoxybenzaldehyde, in situ decarboxylation and intramolecular ring cyclization to construct the tetralone skeleton. Stereospecific reduction of the O-alkylated ketone 13 afforded good yield of precusor alcohol 5. Final coupling of alcohol 5 with 4-hydroxy-coumarin yielded flocoumafen (1). Separation and structure determination of cis- and trans-flocoumafen through 2D NMR analyses-assisted computer simulation techniques for the evaluation of anticoagulant activities are reported for the first time. This method is useful for generating the core tetralone skeleton of 4-hydroxycoumarin derivatives and provides a generalized access to various warfarin type anticoagulants. 相似文献
13.
A facile anionic cyclization approach toward stereocontrolled synthesis of the hexahydrobenzofuran subunit 3 of avermectin is described. As a model study, treatment of iodo compound 7 with n-BuLi at -100 degrees C effected metal-halogen exchange and subsequent anionic cyclization to afford perhydrobenzofuranone 8. For the total synthesis of subunit 3, compound 9 was dihydroxylated to give diol 10. Protection of the hydroxyl groups of diol 10 gave compound 11. Ketone 11 was then converted into the required enone 12 using Saegusa's protocol. On iodination followed by Luche reduction, enone 12 yielded alpha-iodo allylic alcohol 14, which on alkylation afforded ether 15. Conversion of the ester unit of 15 into a Weinreb amide group followed by anionic cyclization gave enone 17. 1,4-Addition of (MeOCH(2))(2)CuCNLi(2) to enone 17 followed by cleavage of the acetal unit afforded ketone 19. Preferential acetylation of the secondary alcoholic function of 19 afforded compound 20. The stereochemistry of 20 is confirmed by single-crystal X-ray analysis. Elimination of HOAc from 20 gave the crucial olefin 21. Hydrolysis of the acetate unit of 21 followed by protection of the resulting alcoholic function yielded tert-butyldimethylsilyl ether 23. Introduction of a hydroxyl group at the ring junction of 23, using Davis's procedure, finally afforded the hexahydrobenzofuran subunit 3. 相似文献
14.
Tokutaro Ogata Yoshiko SugiyamaSaki Ito Kazuha NakanoEri Torii Arisa NishiuchiTetsutaro Kimachi 《Tetrahedron》2013
The first total synthesis of (±)-lantalucratins A and B is described. Introduction of an alkyl side chain at the 6-position was proceeded by directed ortho-lithiation and subsequent alkylation reaction to afford 6-alkyl-5,7,8-trimethoxy-1-naphthol as a synthetically important intermediate for (±)-lantalucratins A and B in excellent yield with complete regioselectivity. The 1,2-naphthoquinone fused five-membered cyclic ether framework was constructed directly from 3-hydroxyalkyl-naphthalenes by oxidative intramolecular cyclization reaction with diammonium cerium(IV) nitrate. (±)-Lantalucratins A and B were obtained in 69% and 45% overall yields, respectively. 相似文献
15.
Brimble MA 《Molecules (Basel, Switzerland)》2004,9(6):394-404
The use of iodobenzene diacetate and iodine under photolytic conditions provides and efficient method for the oxidative cyclization of spiroacetals bearing an hydroxyalkyl side chain to bis-spiroacetals. An overview is provided of the use of this reaction for the synthesis of several bis-spiroacetal containing natural products such as the polyether antibiotics salinomycin and CP44,161 and the shellfish toxins, the spirolides. 相似文献
16.
A simple synthesis of nucleoside analogues with a methylene group between the ribose and 5-position of pyrimidine appendages is outlined. 相似文献
17.
Complex tetrahydrofuran 8, containing the elements of the BC-rings of monensin with four chiral centers, and functionalized for further elaboration, is synthesized via permanganate promoted stereospecific oxidative cyclization of an acyclic, achiral 1,5-diene precursor. 相似文献
18.
Chemistry of Heterocyclic Compounds - A facile one-pot synthesis of N-fused 1,2,4-triazoles from heterocyclic hydrazines and aldehydes is reported. The reaction is efficiently promoted by manganese... 相似文献
19.
20.
Alan R. Katritzky Maria H. Paluchowska John K. Gallos 《Journal of heterocyclic chemistry》1989,26(2):421-426
Benzotriazole mediated synthesis from furfurylamines, aldehydes and lithium acetylides readily provides high yields of N-furfurylpropargylamines. These undergo intramolecular Diels-Alder cyclization to give isoin-doles, which are characterized as their Diels-Alder reaction products with dimethyl acetylenedicarboxylate. 相似文献