定义Definition
有机还原反应是碳原子氧化态降低的反应：增加 C–H 键、减少 C–O（或 C–N、C–X）键，或使不饱和键加氢。常见有催化氢化、金属氢化物还原、溶解金属还原等。
Organic reduction lowers a carbon’s oxidation level: gaining C–H bonds, losing C–O (or C–N, C–X) bonds, or adding hydrogen across multiple bonds — by catalytic hydrogenation, metal hydrides, dissolving metals and more.
主要方法Main methods
①催化氢化（H₂ + Pd/C、Pt、Ni、林德拉催化剂）：还原 C=C、C≡C、硝基、亚胺；②金属氢化物：NaBH₄（醛、酮）、LiAlH₄（还原性更强，可还原酯、酸、酰胺、腈）、DIBAL-H（酯 → 醛）；③溶解金属：伯奇还原、Na/NH₃ 把炔还原为反式烯；④去氧还原：克莱门森、沃尔夫–基斯纳；⑤转移氢化、MPV、不对称氢化。
(1) Catalytic hydrogenation (H₂ with Pd/C, Pt, Ni, Lindlar) for C=C, C≡C, nitro, imines; (2) metal hydrides: NaBH₄ (aldehydes, ketones), LiAlH₄ (also esters, acids, amides, nitriles), DIBAL-H (esters → aldehydes); (3) dissolving metals: Birch, Na/NH₃ for trans-alkenes; (4) deoxygenation: Clemmensen, Wolff–Kishner; (5) transfer hydrogenation, MPV and asymmetric hydrogenation.
化学选择性Chemoselectivity
NaBH₄ 在醇中只还原醛、酮，不还原酯；吕歇还原（NaBH₄/CeCl₃）对烯酮只还原羰基；林德拉催化剂把炔停在顺式烯烃。合理选择试剂是多步合成的关键。
NaBH₄ in alcohol reduces aldehydes and ketones but not esters; Luche conditions (NaBH₄/CeCl₃) reduce only the C=O of enones; Lindlar catalyst stops alkynes at cis-alkenes.
历史History
萨巴蒂埃（1897 年起镍催化氢化，1912 年诺贝尔化学奖）；LiAlH₄（1947）与 NaBH₄（1940 年代，施莱辛格与布朗）的发现使羰基还原变得简便。
Sabatier’s nickel-catalysed hydrogenation (from 1897, Nobel 1912); the discovery of LiAlH₄ (1947) and NaBH₄ (1940s, Schlesinger and Brown) made carbonyl reductions routine.
反应Reactions
视试剂而定
Depends on the reagent
确定所需还原程度。
Decide how far to reduce.
选择化学选择性合适的还原剂。
Choose a reductant with suitable chemoselectivity.
酮还原为仲醇。
A ketone reduced to a secondary alcohol.
反应机理图Mechanism
红色弯箭头表示一对电子的移动方向：从电子来源（孤对电子或化学键）指向电子去向。Red curly arrows show where an electron pair moves: from its source (lone pair or bond) to its destination.
BH₄⁻ 把负氢 H⁻ 转移到羰基碳
BH₄⁻ delivers a hydride to the carbonyl carbon
烷氧负离子
Alkoxide
2-丙醇
Propan-2-ol
年表Timeline
- 1897
萨巴蒂埃发展镍催化氢化
Sabatier develops nickel-catalysed hydrogenation
- 1947
LiAlH₄ 用于有机还原
LiAlH₄ introduced for organic reductions
- 1952
林德拉催化剂
Lindlar catalyst