Chapter 2 c-c formation.ppt

第二章 碳碳键的形成 有机化合物的合成 分子骨架的形成 分子骨架的形成 1.Enolate Alkylations The carbonyl group of an aldehyde or a ketone is an electron-withdrawing group by both induction and resonance. So α-hydrogens to the group possess increased acidity simply due to their proximity and the incipient anion can be stabilized throughπ- resonance with the carbonyl group. Basic Information Basic Information What is carbanion?  If one C=O group helps to stabilize a carbanion, then 2 C=O help to stabilize even more: C-C bond formation 2. 金属有机化合物的反应 金属有机化合物：金属原子与碳原子直接相连的化合物。 Organometallic Journal of Organometallic Chemistry Applied Organometallic Chemistry 金属有机化合物的反应 一、有机镁化合物 格氏试剂（Grignard Reagents） 2)、与羰基的反应 (Reaction with Carbonyl Compounds) （1）、与醛酮的反应 5)、与α，β不饱和醛酮反应 α，β-unsaturated ketones or aldehydes 四﹑有机锌化合物： Reformatsky反应： 用α-卤代羧酸酯在锌的作用下与醛或酮反应，生成β-羟基酸酯，或脱水生成α，β不饱和羧酸酯。 五﹑有机镉试剂 C-C bond formation Mechanisms of aldol: Base-catalyzed aldol: Mechanisms of aldol: Acid-catalyzed adol Aldol Condensation Mixed or cross adol Two solution to this probelm Aldol Condensation Note that the products from acid or base-catalyzed aldols can be different. Mechanism under acidic conditions Mechanism under basic conditions Aldol Condensation Solution 2: Aldol Condensation Aldol Condensation Stereochemistry of the aldol condensation B) Darzen reaction 醛或酮与α-卤代酸酯在碱催化下缩合生成α，β-环氧 羧酸酯的反应称为Darzen缩合。 (C) Claisen Reaction 羧酸酯在碱性催化剂作用下与含有活泼亚甲基的羰基化合物缩合生成β－羰基化合物的反应，总称为Claisen缩合反应． (D)酯-酯缩合 分子间缩合反应（Claisen Condesation） a 酯的自身缩合 (D)酯-酯缩合 分子内酯-酯缩合（Dieckmann Condesation) (E)、 Knoevenagel Reaction　 (F) Michael Additions Michael Additions (G)Mannich Reaction Olefin Synthesis Olefin Synthesis B) Hydroboration C) Hydroalumination with DIBAL: (iBu)2AlH II. Wittig Olefination Wittig Olefination Wittig Olefination Stereochemistry of Wittig reaction Stabilized yildes III. Horner-Wadsworth-Emmons Olefination Horner reaction Masamune-Roush modification: Still modification: Applications in natural prod