15 エステル化・スルホニル化・アミド化・シリル化 : 天然物合成のための汎用反応の実用的合理化(口頭発表の部)
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Esterifications, sulfonylations, amide formations, and silylations are well recognized as frequently used reactions for the natural product synthesis and the process chemistry. As an "endless software development", we introduce herein our recent studies in this area. (i) Esterification, thioesterification, and amide formation using novel condensation agents. We introduce the titled condensations between 1: 1 mixture of carboxylic acids and alcohols, thiols, or amines using Me_2NSO_2Cl / Me_2NR and p-TsCl / N-methylimidazole reagents. These methods are currently utilized in the process chemistry and would be applied to the natural product synthesis. (ii) Pyridine-free sulfonylation methods for alcohols utilizing sterically uncrowded tertiary amine catalysts. As a promising candidates for the replacement of conventional TsCl / pyridine-method (low reactivity, requirement of ca. 10 eqiuv of Py, and prone to the undesirable side chlorides formation), we developed efficient pyridine-free improved methods, which utilized Me_3N・HCl / Et_3N and Me_2N(CH_2)_nNMe_2 as a key protocol. These methods are currently utilized in the natural product synthesis and an industrial scale production of fine chemicals. (iii) Catalytic methods for the preparation of silyl ethers and enol silyl ethers. The presence of catalytic TBAF (0.02 equiv) significantly promoted the silylation of alcohols using a variety of available R_3Si-N, R_3Si-H, and (R_3Si)_2 under mild conditions. A novel mild and powerful silylations agent, Si-BEZAs (silyl benzamides) with pyridinium triflate catalyst is also introduced. An efficient method for the preparation of enol silyl ethers using a novel agent, silazanes with NaH or DBU catalyst is also described, wherein TMS and TBDMS groups were smoothly introduced into ketones and aldehydes under mild conditions.
- 天然有機化合物討論会の論文
- 2005-09-15
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関連論文
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