Systematic Studies on the Role of Lewis Acids in Organic Synthesis.

路易斯酸在有机合成中作用的系统研究。

• 批准号: 04453019
• 负责人: YAMAMOTO Yoshinori
• 金额: $ 4.03万
• 依托单位: TOHOKU UNIVERSITY
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for General Scientific Research (B)
• 财政年份: 1992
• 资助国家: 日本
• 起止时间: 1992 至 1993
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-04453019/
• 关键词: Allyltin; Lewis Acids; Radical Reaction; Radical Initiator; Acyliminium ion; alpha-Alkoxycarbamate; Chelation; Asymmetric Synthesis; アリル有機金属化合物; アリルスズ; フリーラジカル反応; イミニウムイオン; 塩化亜鉛; 立体選択的反応; 14族金属元素; 有機鉛反応剤; クラム-シン選択性; Nーアシルイミニウムイオン; シンクリナル

The reaction of allyltributyltin with methyl 2-[N-((4S)-4-(1-methylethyl)-2-oxazolidinone-3-carbamoyl)amino]-2-bromoacetate was accelerated at -50ﾟC in the presence of AIBN and stopped in the presense of galvinoxyl, indicating that the reaction proceeds through radical mechanism. The reaction was accelerated dramatically at -78ﾟC in the presence of ZnCl_2・OEt_2, and the ZnCl_2-mediated reaction was stopped in the presence of galinoxyl. In the presence of 2 equiv ZnCl_2・OEt_2, the reaction afforded methyl (2R)-2-[N-((4S)-4-(1-methylethyl)-2-oxazolidinone-3-carbamoyl)amino]-4-pentenoate 3a(R) with high diastereoselectivity (93 : 7). Taken together, ZnCl_2・OEt_2 works as a radical initiator as well as chelating agent. The ZnCl_2・OEt_2 mediated reaction of 1,1-diphenylmethyl bromide with allyltributytin gave 4,4-diphenyl-but-1-ene in high yield. On the other hand, no reaction took place between 1,1-diphenylmethyl bromide and BF_3・OEt_2. The ZnCl_2 mediated allylation proceeded in high yiel … More ds in cases of tertiary-, allyli-, alpha-alkoxy, and sec-benzyl-halides, whereas the reacion did not occur with primary and secondary halides. It is proved that the ZnCl_2 mediated allylation of bromomalonate and related compounds proceeds via a radical pathway.The N-acyliminium ion intermediates generated from alpha-alkoxycarbamates in the presence of Lewis acids were for the first time detected by ^1H and ^<13>CNMR.It was confirmed that there is an equilibrium between the starting carbamate and the intermediate, and the equilibrium is highly dependent upon a Lewis acid. By using the saturation transfer method, the rate constant for the formation of the intermediate was obtained. NOE experiments revealed that (4-methylphenylmethylene)methyl(methoxycarbonyl)ammonium methyltrifluoroborate has E-geometry.Lewis acid-base combinations TiCl_4・XPh_3 (X=As, Sb, Bi) have been developed to mediate the Lewis acidity of TiCl_4. The inverse addition of TiCl_4・AsPh_3 to 2-(benezyloxy)propanal and allystannane provided a chelation-controlled product with high diastereoselectivity. Diels-Alder reation of the acrylate of (S)-ethyl lactate with cyclopentadiene in the presence of TiCl_4-SbPh_3 afforted an endo-adduct with high diastereoselectivity and without cyclopentadiene polymerization. Less

丙烯基三丁基锡与甲基2-[N-((4S)-4-(1-methylethyl)-2-oxazolidinone-3-carbamoyl)amino]-2-bromoacetate的反应在-50ﾟC时被加速，而在丙二醛存在下反应停止，表明反应是通过自由基机理进行的。在-78ﾟC下，反应在氯化锌·OEt_2存在下被显著加速，而氯化锌介导的反应在Galinoxyl存在下被终止。在2当量ZnCl2·OEt_2存在下，反应生成了具有高非对映选择性(93：7)的甲基(2R)-2-[N-((4S)-4-(1-methylethyl)-2-oxazolidinone-3-carbamoyl)amino]-4-pentenoate 3a(R)。综上所述，ZnCl2·OEt2既是自由基的引发剂，又是络合剂。以氯化锌为催化剂，1，1-二苯甲基溴与烯丙基三丁烯反应，高产率地合成了4，4-二苯基-1-丁烯。另一方面，1，1-二苯基甲基溴与BF_3·OEt_2不发生反应。氯化锌催化的烯丙化反应在高产率…中进行在叔基、烯丙基、α-烷氧基和仲苯基卤化物的情况下，DS更多，而与伯卤化物和次卤化物的反应不发生。证明了氯化锌催化的溴丙酸及其相关化合物的烯丙化反应是通过自由基途径进行的。在Lewis酸存在下，α-烷氧基氨基甲酸酯生成的N-酰基胺离子中间体首次被~1H和~(13)&gt；CNMR检测到。证实了起始氨基甲酸酯和中间体之间存在平衡，并且平衡高度依赖于Lewis酸。用饱和转移法求出了中间体形成的速率常数。NOE实验表明，(4-methylphenylmethylene)methyl(methoxycarbonyl)ammonium甲基三氟硼酸盐具有E-几何构型。合成了L iCl4·xPh_3(X=As，Sb，Bi)酸碱组合来调节TiCl4的Lewis酸性。TiCl4·AsPh_3与2-(苯氧基)丙醛和尿囊素的反加成反应提供了一个具有高非对映选择性的络合控制产物。在TiCl4-SbPh_3存在下，(S)-乳酸乙酯与环戊二烯发生Diels-Alder反应，得到非对映选择性高的环戊二烯内加合物。较少

项目成果

Y.Yamamoto, J.Yamada, T.Asano: "A New Type of Complex Reagent, R_4Pb/TiCl_4" Tretrahedron Symp.48. 5587-5596 (1992)

Y.Yamamoto、J.Yamada、T.Asano：“一种新型复杂试剂，R_4Pb/TiCl_4”Ttrahedron Symp.48。

Y.Yamamoto, T.Nakada, H.Nemoto: "NMR Detection of N-Acyliminium Ion Intermediates Generated from alpha-Alkoxycarbamates." J.Am. Chem. Soc.114. 121-125 (1992)

Y.Yamamoto、T.Nakada、H.Nemoto：“由 α-烷氧基氨基甲酸酯生成的 N-酰亚胺离子中间体的 NMR 检测。”

N.Shida, T.Uyehara, Y.Yamamoto: "Asymmetric Cyclization via Tandem Conjugate Addition By Using Metal Amide Reagents. Importance of Foldel Orientation of Two Enoate Moieties." J.Org. Chem.57. 5409-5051 (1992)

N.Shida、T.Uyehara、Y.Yamamoto：“使用金属酰胺试剂通过串联共轭加成进行不对称环化。两个 Enoate 部分的 Foldel 方向的重要性。”

V.Gevorgyan, Y.Yamamoto: "Bu_4NF-BF_3・OEt_2 as a New Reagent for the Selective Deprotection of the Enol Ethers of gamma-Alkoxyallylstannanes." J.Chem. Soc. Chem. Commun.59-60 (1994)

V.Gevorgyan，Y.Yamamoto：“Bu_4NF-BF_3·OEt_2 作为γ-烷氧基烯丙基锡烷选择性脱保护的新试剂。J.Chem。”

山本嘉則: "Selective Reactions Using Allylic Metals" Chem.Rev.93. 2207-2293 (1993)

Yoshinori Yamamoto：“使用烯丙基金属的选择性反应”Chem.Rev.93 (1993)。