第7章羰基化合物的亲核加成.ppt

Wittig reaction —— the reaction of an aldehyde or a ketone with a phosphonium ylide to form an alkene. Wittig reaction —— it is completely regioselective, unlike E2 —— it is also stereoselective 顺反烯烃的生成受条件和Ylide试剂的结构、活性等影响很大 The use of Wittig reaction in industry 5. a, b – 不饱和羰基的亲核加成——1，2和1，4加成 关于亲核加成的小结 2. 含O, S亲核试剂 4. 含C亲核试剂 影响因素：(1) 亲核试剂的碱性；(2) 空间位阻 (4) Ylide试剂 (3) 有机金属试剂 (2) ˉC≡CR (1) ˉCN 3. 含N亲核试剂 (1) RNH2 and YNH2 包括H2O, ROH, RSH, 和NaHSO3 1. 概述 —— 结构、机理、反应活性、立体化学 (2) R2NH —— C-C键的形成 羰基的保护 醛酮的分离纯化 亚胺及其衍生物的形成 烯胺的形成 α -羟基腈、α-羟基酸和β-氨基醇 炔醇的合成 C=C的形成 各级醇的合成、醛酮的合成 二、羰基的亲核加成 5. a, b – 不饱和羰基的亲核加成 Both 1,2-addition and 1,4-addition can happen, they are also called as direct addition and conjugated addition 二、羰基的亲核加成 影响 1,2-和1,4-加成的因素 (1) 亲核试剂的碱性 Nucleophiles that are strong bases, such as RLi and LiAlH4, tend to form direct addition products，for the reaction is irrersible. Nucleophiles that are relatively weak bases, such as ˉCN, amines, thiols, and Xˉ, usually form conjugated addition products. 二、羰基的亲核加成 影响 1,2-和1,4-加成的因素 (1) 亲核试剂的碱性 (1) 亲核试剂的碱性 影响 1,2-和1,4-加成的因素 (2) 空间位阻 三、羧酸及其衍生物的亲核取代反应 1. Mechanism for nucleophilic substitution 三、羧酸及其衍生物的亲核取代反应 2. Reaction activity The weaker the base, the better it is as a leaving group The less basic the substituent (Y), the more reactive the carboxylic acid derivative 三、羧酸及其衍生物的亲核取代反应 碱性强弱顺序为： Xˉ RCOOˉ RO ˉ ~ HO ˉ R2N ˉ 反应活性顺序为： 2. Reaction activity 三、羧酸及其衍生物的亲核取代反应 For a carboxylic acid derivative to undergo a nucleophilic acyl substitution reaction, the incoming nucleophile must not be a much weaker base than the group that is to be replaced. A carboxylic acid derivative can be converted into a less reactive carboxylic acid derivative, but not into one that is more reactive. 2. Reaction activity 三、羧酸及其衍生物的亲核取代反应 The R- and H- in aldehydes and ketones, are the strongest base, so, they cannot take place the nucleophilic substitution reaction. Acyl halide and acid anhydrides are not found in nature