H H 3 C CH 3. H Oxirane cis-2,3-dimethyloxirane 1,2-Epoxycyclohexane (Ethylene oxide) (cis-2-butene oxide) (Cyclohexene oxide) Ag 2 CH 2

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1 Epoxides: Structure and omenclature Epoxide( 에폭사이드 ) : 산소가 3- 원자고리에삽입된고리형 ether Reactive than alkyl ether to acidic/basic reagent IUPAC 명 - 간단한 epoxide 는 oxirane( 옥시레인 ) 으로명명하며, epoxide 를치환 기로볼경우는접두어 epoxy 로명명함 관용명 - Alkeneoxide( 옥사이드 ) 2 C C 2 3 C C 3 xirane cis-2,3-dimethyloxirane 1,2-Epoxycyclohexane (Ethylene oxide) (cis-2-butene oxide) (Cyclohexene oxide) 11.8 Synthesis of Epoxides A. Ethylene xide Ethylene oxide 의공업적합성 : 2 C 2 C 2 2 Ag 2 C 2 C 2 B. xidation of Alkenes with Peroxycarboxylic Acids Epoxide 는 alkene 을 peroxycarboxylic acid[ 퍼옥시카복실산, peracid( 과산 )] 를이 용한산화반응으로흔히합성된다. Peroxycarboxylic acid : Mg 2 C 3 C meta-chloroperoxybenzoic acid (MCPBA) 2 Magnesium monoperoxyphthalate (MMPP) Peroxyacetic acid (Peracetic acid)

2 30 Epoxidation of alkene with MCPBA : C 2 2 MCPBA 1,2-Epoxycyclohexane (Cyclohexene oxide) m-chlorobenzoic acid MCPBA의 carbonyl 산소가 의수소를뽑으면서결과적으로음전하성격을띄는산소가 cyclohexene의 C=C 이중결합에첨가를일으켜 3-/5-원자고리 transition state를거쳐서산화가일어난다. 3-원자고리 transition state는평면구조이므로 cis-생성물만얻어진다. stereospecific ( 입체특이성 ) Epoxidation of trans-2-butene with MCPBA C C MCPBA C 3 MCPBA C C C 3 C. Internal ucleophilic Substitution in alohydrins 1) Preparation of halohydrin 2 C 3 C C 2 2 / 2 C 3 C C 2 Bridged chloronium cation Regioselective( 위치선택성 ) reaction C 3 C C 2 1-Chloro-2-propanol

3 31 2) Preparation of epoxide from halohydrin C 3 C C 2 a 2 C 3 C C 2 internal S 2 C 3 C C 2 a a Methyloxirane D. Sharpless Asymmetric Epoxidation Allyl alcohol을 titanium tetraisopropoxide[ti(-iso-pr) 4 ] 및 diethyl tartrate 하에서 tert-butylhydroperoxide(tert-bu) 산화제로반응하였을때 C=C 이중결합의 epoxidation이일어나는반응 R 2 R 1 R 2 R 1 Ti(-iso-Pr) 4 (-)-diethyl tartrate R 3 R 3 Allylic alcohol Ti(-iso-Pr) 4 ()-diethyl tartrate R 2 R 1 R 3 EtC CEt EtC CEt (2S,3S)-(-)-Diethyl tartrate (2R,3R)-()-Diethyl tartrate

4 Reaction of Epoxides Epoxide : 삼각형고리의 angle strain 때문에산성혹은염기성조건에서 ring opening( 고리열림 ) 반응이잘일어남 A. Acid-Catalyzed Ring pening 2 - Ethylene glycol 촉매가 oxirane 의 에 protonation 을일으킨후, 2 친핵체에의한 ring opening 이일어남 Stereochemistry and Regiochemistry of Ring pening of Epoxide 1) 양성자 ( ) 가첨가된 epoxide에친핵체의공격은전형적인 S 2 반응의입체선택성을보이며, 친핵체는이탈기에대하여 anti로공격한다. i) 2 ii) - Cyclopentene oxide trans-1,2-cyclopentanediol 2) 양성자 ( ) 가첨가된비대칭 epoxide 에친핵체의공격은 anti 로일어나면서위 치화학은 S 1 반응에따라 carbocation 이안정한쪽을공격한다. C 3 C 3 2 S 4 1-Methyl-1,2-epoxycyclohexane C 3 C 3 i) C 3 ii) - 2-Methoxy-2-methylcyclohexanol Preparation of cis-/trans-1,2-pentanediol from cyclopentene RC 3 i) ii) 2 s 4 t-bu

5 33 B. ucleophilic Ring pening 염기성조건에서 epoxide는여러가지친핵체와 S 2 메커니즘에의하여고리열림반응이일어난다. 친핵체는비대칭 epoxide에대하여입체장애가적은탄소를공격하며, 친핵체의공격은이탈기에대하여 anti 방향으로일어난다. C 3 C C 2 C 3 a C 3 C C 2 C 3 C 3 C 3 C C 2 C 3 a C 3 a C 3 C 3 Cyclohexene oxide trans-2-methoxycyclohexanol C 3 Reaction of styrene oxide with lithium aluminum hydride(lial 4 ) LiAl 4 / TF Al 3 Li 2 Styrene oxide 1-Phenylethanol Reaction of methyloxirane with various nucleophile / 2 S a S 2 i) -C ii) 2 C a ac 2 3 C 2

6 Ethylene xide and Epichlorohydrin: Building Blocks in rganic Synthesis Ethylene oxide : 2- 탄소골격의작용기를가지며, 반응성이크고가격이저렴하 여유기합성의중요한구성단위화합물로사용됨 C 2 /Pt 2 ac C 3 2 C 3 C 3 C C a C 3 S 2 C 3 2 S C 3 C Ethylene oxide 를이용한 procaine 의합성 2 2 Procaine Epichlorohydrin 의유용성 o C 2 / 2 Ca() 2 3-Chloro-1,2-epoxypropane (Epichlorohydrin) 2 adolol

7 Crown Ethers Crown ether : 고리형 polyether Ethylene glycol(c 2 C 2 ) 의연속적인탈수에의하여합성됨 18-Crown-6 Crown ether의기능 : 고리의산소원자의반복에의해만들어진구멍의지름이알칼리금속의지름과비슷하여산소원자들의비공유전자쌍들이금속이온을효과적으로용매화함. 결과적으로 metal alkoxide에서금속은 crown ether와 chelate를형성하므로음이온이자유롭게되어친핵성의세기가증가함 Sulfides A. omenclature 1) Sulfide(thioether) 의명명 IUPAC 명 : 가장긴모체탄소사슬을선택하고, S를포함한치환체를 alkylsulfanyl( 알킬설파닐 ) 로명명관용명 : S에결합된기 sulfide( 설파이드 ) 2) Disulfide의명명 IUPAC 명 : 가장긴탄소사슬을모체 alkane으로선택하고, disulfide ( 다이설파이드 ) 를포함한치환체를 alkyldisulfanyl 기로명명관용명 : S에결합된기 disulfide S S S S Ethylsulfanylethane 2-Ethylsulfanylpropane Ethyldisulfanylethane (Diethyl sulfide) (Ethyl isopropyl sulfide) (Diethyl disulfide)

8 36 B. Preparation of Sulfides Reaction of haloalkane with a 2 S : 2 R X a 2 S R S R 2 ax 1,4-Dichlorobutane a 2 S a S a S Thiolane a C 3 (C 2 ) 8 C 2 S a C 3 I C 3 (C 2 ) 8 C 2 SC 3 ai Sodium 1-decanethiolate 1-Methylsulfanyldecane (Decyl methyl sulfide) C. xidation of Sulfides S C o C S C 3 ai 4 25 o C S C 3 Methyl phenyl sulfide Methyl phenyl sulfoxide Methyl phenyl sulfone

9 37 Problems Physical Properties Solubility to 2 Preparation of Ethers Williamson synthesis (b) (e) Reactions of Ethers (c) Structure of product I reflux Synthesis and Reactions of Epoxides Reaction mechanism of 1,4-dioxane synthesis 1,4-Dioxane

10 Mechanism of rearrangement BF 3 Tetramethyloxirane 3,3-Dimethyl-2-butanone Synthesis cis-3-exene (a) meso 3,4-hexanediol (b) racemic 3,4-hexanediol Styrene 1-Chloro-3-methyl-2-butene