1、3 Reduction 還原反應(yīng)還原反應(yīng)3.1 Reduction with complex metal hydrides 金屬氫金屬氫化物的配合物化物的配合物3.2 Alkoxyaluminate 烷氧基鋁化物烷氧基鋁化物 reducing agents3.3 Reductions with borohydride 硼氫化物硼氫化物3.4 Borane, aluminum and derivatives 硼烷，鋁烷的硼烷，鋁烷的衍生物衍生物3.5 Catalytic hydrogenation 催化氫化催化氫化3.6 Dissolving metal reductions 可溶性金屬還原可溶

2、性金屬還原3.7 Non-metal reducing agents 非金屬還原劑非金屬還原劑 3.1.1 Mechanism 機理機理 3.1.2 Reduction of carbonyl compounds 羰基化羰基化合物合物 3.1.3 Reduction of non-carbonyl heteroatom functional group 無羰基的雜原子官能團無羰基的雜原子官能團3.1 Reduction with complex metal hydrides3.1.1 Mechanism3.1.2 Reduction of carbonyl compounds酰胺羰基被還原成亞

3、甲基酰胺羰基被還原成亞甲基,-unsaturated carbonyl derivatives 不飽和羰基化合物不飽和羰基化合物Conjugated ketones 共軛酮 often result conjugate reduction(14);conjugated aldehydes 共軛醛 often result 1,2 reduction (13).3.1.3 Reduction of non-carbonyl heteroatom functional group Epoxides 環(huán)氧 Ozonides 臭氧化物 Nitriles 氰 Azides 疊氮 Nitro compou

4、nds 硝基化合物 Alkyl halides 鹵代烴 Sulfonate esters 磺酸酯 Alkyne alcohols 炔烴3.1.3.1 EpoxidesLithium aluminum hydride delivers the hydride to the less sterically encumbered carbon 位阻小的碳 of an epoxide.3.1.3.2 Ozonides 臭氧化物臭氧化物 and Nitriles 氰氰3.1.3.3 Azides 疊氮化物疊氮化物3.1.3.4 Nitro compounds 硝基化合物硝基化合物3.1.3.5 Alky

5、l halidesBenzylic halides 芐鹵芐鹵 aliphatic halides 脂肪鹵脂肪鹵 aryl halides 芳鹵芳鹵H-作為親核試劑，作為親核試劑，SN2反應(yīng)。反應(yīng)。3.1.3.6 Sulfonate esters 磺酸酯磺酸酯3.1.3.7 Alkyne alcoholsIn general, the alkene and alkynyl moieties are not reduced by LiAlH4.3.2 Alkoxyaluminate reducing agentsThe reactivity of the LiAlH4 is progressive

6、ly reduced when it is reacted with alcohols. 四氫鋁鋰的還原四氫鋁鋰的還原性隨著它與醇的反應(yīng)逐漸減小。性隨著它與醇的反應(yīng)逐漸減小。Example Red-Al The reducing power of Red-Al is close to lithium aluminum hydride.和四氫鋁鋰近似Advantages: Good thermal 熱 stability and easy solubility in aromatic hydrocarbon.芳烴溶劑雙甲氧乙氧基鋁氫化物雙甲氧乙氧基鋁氫化物Example 3.3 Reductio

7、ns with borohydride Sodium borohydride 硼氫化鈉硼氫化鈉 Alternative metal borohydrides (Li, Zn, Ce)其其它金屬硼氫化物它金屬硼氫化物 Alkoxy- and alkylborohydrides 烷氧基，烷基烷氧基，烷基硼氫化物硼氫化物3.3.1 Sodium borohydrideSodium borohydride is less reactive 還原性較弱還原性較弱 than lithium aluminum hydride, making it a very selective reagent 選擇性還原

8、劑選擇性還原劑, reducing ketones, aldehydes, and acid chlorides 醛酮酰氯醛酮酰氯 in the presence of other reducible functional groups.Example Aqueous and alcohol solvents 水或醇溶劑水或醇溶劑 are preferred due to the excellent solubility .One of the more important uses of NaBH4 is the reduction of enamines烯胺烯胺, imines亞胺亞胺,

9、and iminium salt亞胺鹽亞胺鹽, particularly useful in alkaloid 生物堿生物堿 and amino acid 氨基酸氨基酸 syntheses .3.3.2 Alternative metal borohydrides (Li, Zn, Ce)其他的金屬硼氫化物其他的金屬硼氫化物L(fēng)iBH4 is a more powerful reducing agent 更強的還原劑 than NaBH4. It can reduce aldehydes, ketones, acid chloride, epoxides環(huán)氧, esters酯 and lacto

10、nes 內(nèi)酯.It can not reduce acids, nitriles氰基化合物, or nitro compounds硝基化合物.Example 3.3.3 Alkoxy- and alkylborohydrides 烷烷氧基和烷基硼氫化物氧基和烷基硼氫化物 Acyloxyborohydrides 乙氧基硼氫化物乙氧基硼氫化物 Super Hydrides 超級氫化物超級氫化物 The selectrides 三仲丁基硼氫化物三仲丁基硼氫化物 Sodium cyanoborohydrides 氰基硼氫化氰基硼氫化鈉鈉3.3.3.1 Acyloxyborohydrides 酰氧基硼氫

11、化物酰氧基硼氫化物Acyloxyborohydrides are remarkably selective.非常高的選擇性非常高的選擇性3.3.3.2 Super Hydrides 超氫化物超氫化物The most common use of Super-Hydrides is probably for the reductive dehalogenation of alkyl halides. 用于用于鹵代烴的脫鹵化反應(yīng)。這個是氫負離子作為親核試鹵代烴的脫鹵化反應(yīng)。這個是氫負離子作為親核試劑的劑的SN2反應(yīng)，印證了這類化合物的強還原性。反應(yīng)，印證了這類化合物的強還原性。3.3.3.3 The

12、 selectrides3.3.3.4 Sodium cyanoborohydridesA remarkably stable regent that does not decompose in acid solution. 非常穩(wěn)定，酸性條件下仍能穩(wěn)定存在。非常穩(wěn)定，酸性條件下仍能穩(wěn)定存在。還原氨化反應(yīng)，亞胺的還原。還原氨化反應(yīng)，亞胺的還原。酸性條件下進行酸性條件下進行+BrBr+BrBr+Br2KOHH2/ NiBlanc Chloromethylation Reaction （Blanc氯甲基化反應(yīng)氯甲基化反應(yīng) ）Blanc 氯甲基化反應(yīng)是指在Lewis 酸催化下,芳香族化合 物和 HC

13、l ,甲醇或氯甲醚反應(yīng) , 在芳香族化合物中引入氯甲 基,這一反應(yīng)在有機合成和化工生產(chǎn)中有重要的應(yīng)用. HCl的作用：（1）提供氫離子讓甲醛質(zhì)子化，然后對苯環(huán)進攻；（2）提供氫離子讓苯甲醇中間體羥基質(zhì)子化；（3）提供氯離子對質(zhì)子化的苯甲醇進攻發(fā)生SN2反應(yīng) OO1，3-丁二烯和順丁烯二酸酐為原料OOBaeyer- VilligerOOHOOCOEtOOCEtOOCEtOOCHOOCHOOCP, HIOHOHOOO+OOOOOEtOOCHOOCHOOCOHOHOOO+OOOLiAlH4Et2OPHI1) O32) H2O2CH3CH2OHH+, EtOOCEtOOCCH3ONaCH3OH1) O

14、H-2) H+3) CH3COOOHOO布洛芬布洛芬3.4 Borane 硼烷硼烷, aluminum hydride and derivatives 氫化鋁及其衍生物氫化鋁及其衍生物 Borane Aluminum hydride and derivatives3.4.1 BoraneDiborane 乙硼烷 is a potent 強效的 reducing agent 還原試劑 for aldehydes醛, ketones酮, lactones內(nèi)酯, epoxide環(huán)氧, acids酸, tertiary amides 三級酰胺 and nitriles腈. It is ineffect

15、ive for the reduction of esters and reacts with alkene.對酯的還原和與烯烴反應(yīng)效果不佳。 由于硼烷的缺電子特性，強路易斯酸，能夠與富電子的原子配位結(jié)合。在由于硼烷的缺電子特性，強路易斯酸，能夠與富電子的原子配位結(jié)合。在還原羰基時，增加羰基的電子云密度有利于反應(yīng)的進行，比如新戊醛反應(yīng)比還原羰基時，增加羰基的電子云密度有利于反應(yīng)的進行，比如新戊醛反應(yīng)比三氯乙醛容易還原。三氯乙醛容易還原。3.4.2 Aluminum hydrideIts most common use is the selective 1,2-reduction of conj

16、ugated aldehydes, ketones and esters.選擇性的選擇性的進行進行1,2還原對于共軛的醛酮和酯。還原對于共軛的醛酮和酯。果蠅信息素合成中間體果蠅信息素合成中間體氫化鋁作為路易斯酸與氧配位結(jié)核性強，同時空間距離決定了負氫轉(zhuǎn)移到羰基碳比位容易。3.4.3 Diisobutylaluminum hydride 二異丁二異丁基氫化鋁基氫化鋁將酰胺還原成醛將酰胺還原成醛將酯還原成醛3.5 Catalytic hydrogenation 催化氫化催化氫化 Heterogeneous 非均相非均相: catalyst insoluble 不溶不溶 in the reactio

17、n medium 反應(yīng)介質(zhì)反應(yīng)介質(zhì). Homogeneous 均相均相: catalyst soluble in the reaction medium. 3.5.1 Typycal heterogeneous hydrogenation catalysts3.5.2 Heterogeneous hydrogenation reductionsRCH=CHR + H2RCH2CH2RcatalystuCatalyst 催化劑催化劑: Pt, Pd, NiuPd/C: Palladium on carbon 鈀負載在碳上鈀負載在碳上uRaney Ni: Al-Ni reacts with NaO

18、HuHeat of hydrogenation: higher H, higher potential energy of alkeneuSyn addition 順式加成順式加成Why syn addition?H2HHHHMechanism of hydrogenation:uAlkyne is more reactive than alkene;uLindlar catalyst: Pd/CaCO3uSyn addition product: cis-alkeneHow to get trans-alkene 反式烯烴反式烯烴?3.5.3 Homogeneous CatalysisSol

19、uble homogeneous catalysts offer the best route for asymmetric induction 不對稱氫化不對稱氫化 in catalytic hydrogenation, especially for alkenes.Wilkinsons catalystExample A common way to generate a chiral catalyst involves a modification of Wilkinsons catalyst.One of the more important applications of chiral

20、 hydrogenation catalysts is the preparation of chiral amino acids.3.6 Dissolving metal reductionsReduction of carbonyl compounds 羰基化合物羰基化合物Reduction of alkynes 炔烴炔烴Hydrogenolysis 氫解氫解Birch reduction 還原還原The Benkeser reductionReduction with zinc and tin 鋅和錫鋅和錫Reduction with aluminum 鋁鋁Electrolytic re

21、ductions 電解還原電解還原3.6.1 Reduction of carbonyl compoundsClemmensen 還原還原3.6.2 Reduction of alkynes 非末端炔烴非末端炔烴Anhydrous ammonia (NH3) is a liquid below -33 C Alkali metals 堿金屬堿金屬 dissolve in liquid ammonia and function as reducing agents 有還原劑的作用有還原劑的作用Alkynes are reduced to trans-alkenes with sodium 鈉鈉

22、or lithium 鋰鋰 in liquid ammoniaThe reaction involves a radical anion 自由基負離子自由基負離子 intermediateNaRCCRNH2RCCRHCCRHRHCRCRHRCCRHNaCCRHRvinyl radical I IIanion radicalMechanism of dissolved metal reduction:3.6.3 Hydrogenolysis 氫解氫解Dissolving metal conditions are particularly useful for the cleavage of O-

23、benzyl and N-benzyl deritives.芐氧基，芐氮基，去保護。芐氧基，芐氮基，去保護。開環(huán)丙烷環(huán)開環(huán)丙烷環(huán)除去砜基除去砜基氧位于位阻小的一邊氧位于位阻小的一邊3.6.4 Birch reduction與芳環(huán)共軛的雙鍵會被還原掉與芳環(huán)共軛的雙鍵會被還原掉An important modification of Birch reduction is replacing lithium with calcium, called Benkeser reduction.總體和總體和Birch一樣，安全性更好。一樣，安全性更好。3.6.5 The Benkeser reduction3.6.6 Reduction with zinc and tinZinc in acetic acid is a very effective reagent