99488-10-5Relevant academic research and scientific papers
Ruthenium-porphyrin-catalyzed diastereoselective intramolecular alkyl carbene insertion into C-H bonds of alkyl diazomethanes generated in situ from N-tosylhydrazones
Reddy, Annapureddy Rajasekar,Zhou, Cong-Ying,Guo, Zhen,Wei, Jinhu,Che, Chi-Ming
, p. 14175 - 14180 (2015/01/09)
With a ruthenium-porphyrin catalyst, alkyl diazomethanes generated in situ from N-tosylhydrazones efficiently underwent intramolecular C(sp3)-H insertion of an alkyl carbene to give substituted tetrahydrofurans and pyrrolidines in up to 99% yield and with up to 99:1 cis selectivity. The reaction displays good tolerance of many functionalities, and the procedure is simple without the need for slow addition with a syringe pump. From a synthetic point of view, the C-H insertion of N-tosylhydrazones can be viewed as reductive coupling between a C=O bond and a C-H bond to form a new C-C bond, since N-tosylhydrazones can be readily prepared from carbonyl compounds. This reaction was successfully applied in a concise synthesis of (-)-pseudoheliotridane.
On the stereoselectivity of γ-lactol substitutions with allyl- and propargylsilanes - Synthesis of disubstituted tetrahydrofuran derivatives
Schmitt, Andreas,Reissig, Hans-Ulrich
, p. 3893 - 3901 (2007/10/03)
Monosubstituted γ-lactols 1a-1c, 3a-3c and 4a-4c, as well as disubstituted γ-lactol 5 and the γ-hydroxy-substituted γ-lactone 6, were transformed into disubstituted tetrahydrofuran derivatives by treatment with allyl- and propargylsilanes in the presence of Lewis acids. The diastereoselectivities were moderate to excellent and are interpreted by application of the Felkin-Anh model to cyclic oxocarbenium ions. The effects of the equilibria between conformers of the intermediates are discussed. The surprisingly high diastereoselectivity of 4-substituted γ-lactols 3 can be explained on this basis.
Highly Stereoselective Synthesis of cis-2-Substituted-3-vinyltetrahydrofurans from (Z)-Trimethyl(5-trimethylsiloxy-2-pentenyl)silane and Acetals
Sano, Tomohumi,Oriyama, Takeshi
, p. 716 - 718 (2007/10/03)
A variety of cis-2-substituted-3-vinyltetrahydrofurans are easily and stereoselectively produced by the reaction of acetals with (Z)-trimethyl(5-trimethylsiloxy-2-pentenyl)silane under the influence of a catalytic amount of trimethylsilyl trifluoromethanesulfonate under very mild conditions.
Reduction of Cyclic Hemiacetals. The Synthesis of Demethoxyeleutherin and Nanaomycin A
Kraus, George A.,Molina, Maria Teresa,Walling, John A.
, p. 1568 - 1569 (2007/10/02)
The reduction of cyclic hemiacetals containing two stereogenic centres is highly stereoselective.
Diastereoselective Synthesis of cis- or trans-2,3-Substituted Tetrahydrofurans and 3,4-Substituted 4-Butanolides
Frauenrath, Herbert,Philipps, Thomas
, p. 1951 - 1961 (2007/10/02)
Improved synthesis of 10 and the epimerisation 10 --> 11 yield cis- and trans-tetrahydro-3-furancarbaldehydes (10,11) with high diastereoselectivity. 10 as well as 11 are reduced by the Wolff-Kishner procedure to give 2-substituted 3-methyltetrahydrofurans 15 with trans configuration. 2-Substituted 3-methyltetrahydrofurans with cis configuration 14 are synthesized via 10 --> 12 --> 13 --> 14.The furans 14 and 15 possess structural features of naturally occurring 4-butanolides like quercus lactone a, quercus lactone b, or eldanolide which is the pheromone of the sugarcane borer Eldana saccharina (Wlk.). 14 and 15 are readily oxidized with CrO3/Ac2O to yield the lactones 16 and 17, whereas oxidation with Ru oxides proved to be less effective.The synthesis of rac-1 and rac-2 is described.
