排序方式: 共有37条查询结果,搜索用时 46 毫秒
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Akira Yanagisawa Prof. Dr. Takahiro Suzuki Takanori Koide Shogo Okitsu Takayoshi Arai Prof. Dr. 《化学:亚洲杂志》2008,3(10):1793-1800
A Barbier‐type regioselective propargylation of aldehydes and ketones with (3‐bromobut‐1‐ynyl)trimethylsilane has been achieved using reactive barium as a low‐valent metal in THF. Especially in the case of ketones, the corresponding homopropargylic alcohols form almost exclusively. In the reaction of α,β‐unsaturated carbonyl compounds, only 1,2‐adducts have been observed. This method is also applicable to propargylation of imines, and the corresponding homopropargylic amines are obtained regiospecifically in good yields with diastereomeric ratios of up to 87:13. 相似文献
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J.S. Yadav B.V. Subba Reddy P. Vishnumurthy Swapan Kr. Biswas 《Tetrahedron letters》2007,48(38):6641-6643
α-Diazoketones undergo smooth allylation with successive bromide insertion with allylindium bromide generated in situ from allyl bromide and indium metal to produce 1-bromo-2-alkyl- or 2-arylpent-4-en-2-ols in high yields. Addition of propargylindium bromide produces 1-bromo-2-alkyl-or 2-arylpent-4-yn-2-ols under similar conditions. 相似文献
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Substituent effects on the SmI2/Pd(0)-promoted carbohydrate ring-contraction of 5-alkynylpyranosides
The effect of substituents on the reactivity and stereoselectivity of the SmI2/Pd(0)-promoted ring-contraction of 5-alkynylpyranosides has been examined using substrates substituted only at selected positions. While formation of 2-ethynylcyclopentanols takes place efficiently, an internal alkyne did not afford the expected product. The presence of peripheral alkoxy substituents leads to variable stereoselectivities that depend on the number and orientation of such groups. Thus, an isolated OBn substituent at C(3) (carbohydrate numbering) exerts a significant stereochemical control while additional substitution with the same group at C(4) either enhances or drastically reduces stereoselectivity depending on its orientation (α or β, respectively). 相似文献
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Theresa M. Locascio Prof. Dr. Jon A. Tunge 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(50):18140-18146
The palladium(0)‐catalyzed, ligand‐controlled, regioselective addition of diaryl acetonitrile pronucleophiles to propargylic carbonates is reported. Selective formation of either terminal 1,3‐dienyl or propargylated products is proposed to arise from a change in reaction mechanism controlled by the denticity of the coordinating ligand. 相似文献
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Introduction of the propargyl dicobalt hexacarbonyl moiety onto the estradiol A ring as a potential probe in receptor studies requires protection of the ring phenolic group, and the regio-selectivity of the attack (2- versus 4-position) depends on the bulkiness of the organometallic carbenium ion. 相似文献
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An electron-rich phosphine additive is critical and sufficient for propargyl-selective couplings of propargylcopper reagents and alkenyl halides. This method is complementary to those previously described, in which high allenyl selectivity is observed in analogous coupling reactions. While the basis of the phosphine effect requires further investigation, the information gained in these studies enables the synthesis of complex molecules by way of skipped enyne intermediates. 相似文献
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Patman RL Williams VM Bower JF Krische MJ 《Angewandte Chemie (International ed. in English)》2008,47(28):5220-5223
10.
J.S. Yadav B.V. Subba Reddy Swapan Kumar Biswas Sandip Sengupta P. Vishnumurthy 《Tetrahedron letters》2008,49(6):1034-1036
Phenacyl bromides undergo smooth vic-diallylation and dipropargylation with allyl and propargyl indium reagents generated in situ from metallic indium and allyl or propargyl bromide to produce 4-arylocta-1,7-dien-4-ol derivatives in good yields. Phenacyl chloride and azide also participated effectively in bis-allylation. Similar results are also obtained from in situ generated allyl or propargyl zinc bromide. 相似文献