Reduction. Ø Hydrogenation. Ø Boron Reagents. Ø Aluminium Reagents. Ø Tin Hydrides. Ø Silanes. Ø Dissolving Metal Reductions. Ø Diimide Reductions

Transcription

1 eduction Ø ydrogenation Ø Boron eagents Ø Aluminium eagents Ø Tin ydrides Ø Silanes Ø Dissolving Metal eductions Ø Diimide eductions C- 423 Course on rganic Synthesis; Course Instructor: Krishna P. Kaliappan 1

2 eduction Catalytic ydrogenation eterogeneous omogeneous C- 423 Course on rganic Synthesis; Course Instructor: Krishna P. Kaliappan 2

3 eduction eterogeneous Catalytic ydrogenation Transition metals adsorbed onto a solid support Metal- Pd, Pt, h, Ni Support- Charcoal, Alumina, Silica Solvents- Me, Et, EtAc, Ac, Et 2, exanes Decreasing order of activity 2, h/al 2 3 2, Pt-C 2, Pd-C 2, a-ni Decreasing order of reactivity CCl N 2 CN C- 423 Course on rganic Synthesis; Course Instructor: Krishna P. Kaliappan 3

4 eduction eterogeneous Catalytic ydrogenation Properties: educes olefins & acetylenes to saturated hydrocarbons Sensitive to steric effects & choice of solvents Polar functional groups, like hydroxyl groups can sometimes direct the delivery of 2 cis-addition of 2 Catalysts can be poisoned 2, Catalyst 1-30 atm rder of solvent reactivity is- exane < EtAc < Et < Ac < Ac/Cl C- 423 Course on rganic Synthesis; Course Instructor: Krishna P. Kaliappan 4

5 eduction eterogeneous Catalytic ydrogenation Mechanism: Catalyst surface Isomerization C- 423 Course on rganic Synthesis; Course Instructor: Krishna P. Kaliappan 5

6 eduction eterogeneous Catalytic ydrogenation Decreasing order of eactivity: FACILE Cl C N 2 N 2 C C C C 2 C 2 C 2 C C() DIFFICULT CN C 2 N 2 C CN C - C 2 + C 2 N INET C- 423 Course on rganic Synthesis; Course Instructor: Krishna P. Kaliappan 6

7 eduction eterogeneous Catalytic ydrogenation Pt/ 2 70% 30% Equatorial attack is predominant C 3 C 3 2, Pd-C C 3 major C 3 + minor C 3 C 3 ydrogen will approach from exo side Ac N S N Ac (C 2 ) 4 CMe Pd/ C/ 2 85 o C 37 bar Ac N S N Ac (C 2 ) 4 CMe 2, Pd-C Bn 3 C + C- 423 Course on rganic Synthesis; Course Instructor: Krishna P. Kaliappan 7

8 eduction eterogeneous Catalytic ydrogenation Directed eterogeneous ydrogenation: 2, Pd-C + major minor ydroxyl group delivers hydrogen from same side 2 / Pd/ C Me Me 2 / Pd/ C C 2 Me C 2 Me Ni/ 2 (95:5) C- 423 Course on rganic Synthesis; Course Instructor: Krishna P. Kaliappan 8

9 eduction of aryl groups: eduction eterogeneous Catalytic ydrogenation 2 / aney Ni 150 o C 2 / aney Ni 200 o C aney Nickel Desulfurization: S S S S 2, a-ni Et C 3 osenmund eduction: Quinoline is used to poison the catalyst to reduce its activity 2, Pd CCl C BaS 4 C- 423 Course on rganic Synthesis; Course Instructor: Krishna P. Kaliappan 9

10 eduction eterogeneous Catalytic ydrogenation Lindlar Catalyst (Pd/CaC 3 ): TMS 2, Pd CaC 3 TMS 2, Pd Me 2 C CaC 3 Me 2 C Lindlar Catalyst 8π con Electrocyclic reaction 6π dis Electrocyclic reaction C- 423 Course on rganic Synthesis; Course Instructor: Krishna P. Kaliappan 10

11 eduction omogeneous Catalytic ydrogenation Mechanism: L n M 2 L n M L n M + L M - L L n-1 Wilkinson's catalyst [(PPh 3 ) 3 hcl] eactivity: C- 423 Course on rganic Synthesis; Course Instructor: Krishna P. Kaliappan 11

12 eduction omogeneous Catalytic ydrogenation 2, (PPh 3 ) 3 hcl 2, (PPh 3 ) 3 hcl 2, (PPh 3 ) 3 hcl Na/ Liq. N 3 N 2 2 / Pt N 2 2 N 2 Et Wilkinson's catalyst SPh 2 (PPh 3 ) 3 hcl SPh C- 423 Course on rganic Synthesis; Course Instructor: Krishna P. Kaliappan 12

13 eduction omogeneous Catalytic ydrogenation Directed omogeneous ydrogenation: K K (PPh 3 ) 3 hcl Me 2 / Et Me C 2 Me C 2 Me (PPh 3 ) 3 hcl Me 2 / Et Me C- 423 Course on rganic Synthesis; Course Instructor: Krishna P. Kaliappan 13

14 Allylic ethers: eduction ydrogenolysis 2/ Pd or Pt - 2 / Pt Et 54% 46% Benzyloxy groups: Bn 2 / Pd Na/ N 3 C- 423 Course on rganic Synthesis; Course Instructor: Krishna P. Kaliappan 14

15 Benzyloxy carbonyl groups: eduction ydrogenolysis alides: 2 N C Br C 2 Ph 2 / Pd Et 2 / Pd - Toluene - C 2 2 N Cl 2 / PdS 4 ther reactions: 3 C N 2 / Pd 3 C N 2 / Pd-C N 2 N 2 C- 423 Course on rganic Synthesis; Course Instructor: Krishna P. Kaliappan 15

16 eduction Boron Based eagents Ø NaB 4 Ø NaB 4 /CeCl 3 Ø NaB 4 / NiCl 2 Ø LiB 4 Ø Boranes Ø NaCNB 3 Ø Zn(B 4 ) 2 Ø NaB(Ac) 3 Ø Me 4 NB(Ac) 3 Ø Alkyl borohydrides C- 423 Course on rganic Synthesis; Course Instructor: Krishna P. Kaliappan 16

17 eduction Boron Based eagents NaB 4 Temperature: 0-25 o C Solvents: Et, Me, Dimethoxy ethane (DME) Substrate: C, C, CCl, 2 C=N Mechanism: B B C- 423 Course on rganic Synthesis; Course Instructor: Krishna P. Kaliappan 17

18 Selectivity: eduction Boron Based eagents NaB 4 N 2 N 2 Luche eduction: 0.25 eq NaB 4 0 C, Et NaB % 10-20% NaB 4 / CeCl 3 (1:1) Me 100% 0% CeCl 3 is a good Lewis acid & highly oxophilic NaB 4 CeCl 3 C- 423 Course on rganic Synthesis; Course Instructor: Krishna P. Kaliappan 18

19 eduction Boron Based eagents Selective reduction of ketones in presence of aldehydes: C C 2 Me NaB 4, CeCl 3 Et, 2 C C 2 Me CeCl 3, 2 C 2 Me (1) NaB 4, CeCl 3 (2) Work up C NaB 4, CeCl 3 C Et, 2 C- 423 Course on rganic Synthesis; Course Instructor: Krishna P. Kaliappan 19

20 eduction of imines: eduction Boron Based eagents 1 3 N Å MS 1 NaB 4 or N N 2 2 / Pd-C 3 C N NaB 4 No eaction NaB 4 can t reduce CN unless Meerwein s salt (Me 3 + BF 4- ) is used CN NaB 4 Me 3 + BF - 4 C N Me BF 4 - C N Me BF - 4 NaB 4 N Me DMS NaC 3 C 2 Br NaB 4 DMS C 3 2 C S C- 423 Course on rganic Synthesis; Course Instructor: Krishna P. Kaliappan 20

21 eduction Boron Based eagents LiB 4 More reactive than NaB 4 but milder than LiAl 4 in ether igher reactivity is due to greater Lewis acid strength of Li + Can reduce esters & lactones efficiently LiB 4 C 3 7 C 3 7 CC 3 C 3 LiB 4 N 2 N 2 C- 423 Course on rganic Synthesis; Course Instructor: Krishna P. Kaliappan 21

22 eduction B CN Na + Boron Based eagents NaB 3 CN At p 3-4, It reduces aldehydes & ketones At p 6-8, It reduces iminium ions Less reactive than NaB 4. Used predominantly in reductive aminations (Borsch eduction) Electron withdrawing cyano group decreases the ease of hydrogen transfer NaB 3 CN reduced iminium ions much more quickly than ketone or aldehyde Uses: ' 2 N, Me N 4 Ac, p=6 ' N ' NaCNB 3 ' N ' C- 423 Course on rganic Synthesis; Course Instructor: Krishna P. Kaliappan 22

23 eduction Boron Based eagents N C N 2, Me N 4 Ac NaCNB 3 N N eduction of oximes: N 4 Br NaCNB 3 Me NaCNB 3 N p=3 α,β-unsaturated ketones: (1) TsNN 2, + N N (2) NaCNB 3 C- 423 Course on rganic Synthesis; Course Instructor: Krishna P. Kaliappan 23

24 eduction Boron Based eagents eduction of tosylhydrazones: (1) TsNN 2, + (2) NaCNB 3 Epoxide openings: NaCNB 3 BF 3.Et 2, TF Drawback: Sometimes strong acids can release CN from NaCNB 3 C- 423 Course on rganic Synthesis; Course Instructor: Krishna P. Kaliappan 24

25 eduction Boron Based eagents Boranes B B 3.TF B SMe 2 B 3.SMe 2 B B B Borane exists as a dimer Borane is highly electrophilic. So, they attack the most electron rich center 1 / 3 B 3 TF Similarly between an amide and ester, amide gets reduced first C- 423 Course on rganic Synthesis; Course Instructor: Krishna P. Kaliappan 25

26 eduction Boron Based eagents Me 1 / 3 B 3 Me 1 / 3 B 3 Me N TF N TF N Me Me Me Me Me 3 B N 3 B N Me Me Me N Me Me Me Me N B N Me 2 B N Me Me C- 423 Course on rganic Synthesis; Course Instructor: Krishna P. Kaliappan 26

27 eduction Boron Based eagents B 3 reduces carboxylic acids to primary alcohols in the presence of esters, nitro and cyano groups C 2 B 3. Me 2 S TF ydroboration: B B 2 B Na ' B 2 6 ' ' 3 + B 2 B B B B' 2 Na ' C 2 C C- 423 Course on rganic Synthesis; Course Instructor: Krishna P. Kaliappan 27

28 B B 2 6 B Catechol borane B eduction Boron Based eagents ther available boranes B 3 B 3 2 B 9BBN Disiamyl borane(sia 2 B) B B B Thexyl borane B B Pinylborane Alpine borane (Ipc) 2 BCl B B B BCl 2 2 C- 423 Course on rganic Synthesis; Course Instructor: Krishna P. Kaliappan 28

29 Borolane B eduction Boron Based eagents Asymmetric reduction of ketones: Alpine Borane Alpine-borane xazaborolidine Ph Ph N B Works best for aryl & acetylenic ketones. Because of steric hindrance it is fairly unreactive TF, 0 o C 94% ee B L S S L C- 423 Course on rganic Synthesis; Course Instructor: Krishna P. Kaliappan 29

30 eduction Boron Based eagents Chlorodiisopinylcamphenyl borane (DIP-Cl) B Cl 2 Chlorine increases the Lewis acidity of boron making it more reactive Saturated ketones are reduced to chiral alcohols with varying degrees of ee Ipc 2 B-Cl TF > 90% ee C- 423 Course on rganic Synthesis; Course Instructor: Krishna P. Kaliappan 30

31 eduction Boron Based eagents xazaborolidine Ph Ph N B Stoichiometric Ph Ph B 3 N B C 3 Catalytic C 2 N 2 Steps Ph Ph N (MeB) 3 Toluene Ph Ph N B Me B 3 Ph Ph N B S L 2 2 B S L Ph Ph C- 423 Course on rganic Synthesis; Course Instructor: Krishna P. Kaliappan N B B Me S L 3 B S L Me 31

32 eduction Boron Based eagents xazaborolidine > 90% ee > 95% ee Br Br > 96% ee C- 423 Course on rganic Synthesis; Course Instructor: Krishna P. Kaliappan 32

33 Uses: Ar N 2 Ar N 2 Ar N Ar N 2 eduction Boron Based eagents NaB 4 / NiCl 2 2 Ar C N Ar C N 2 Preparation: Zn(B 4 ) 2 ZnCl 2 (Ether) NaB 4 Zn(B 4 ) 2 Good for base sensitive groups Chelation control model C- 423 Course on rganic Synthesis; Course Instructor: Krishna P. Kaliappan 33

34 eduction Boron Based eagents Zn(B 4 ) Zn 2+ B Zn(B 4 ) 2 Et 2 Me Zn 2+ Me Zn 2+ C- 423 Course on rganic Synthesis; Course Instructor: Krishna P. Kaliappan 34

35 eduction Boron Based eagents NaB(Ac) 3 ; Me 4 NB(Ac) 3 C Bu 4 NB(Ac) 3 Ph C Bu 4 NB(Ac) 3 Ph Ac B Ac Ph Na + (Ac) 3 B - ipr Ac B Ac C- 423 Course on rganic Synthesis; Course Instructor: Krishna P. Kaliappan 35

36 Selectrides: eduction Boron Based eagents Alkyl Borohydrides M B 3 M + = Li (L-Selectride) = K (K-Selectride) Me L- Selectride TF Me 1 2 L- Selectride TF 1 2 K- Selectride K- Selectride TF Br C- 423 Course on rganic Synthesis; Course Instructor: Krishna P. Kaliappan 36

37 LiBEt 3 (Superhydride): eduction Boron Based eagents Alkyl Borohydrides Very reactive hydride source educe ketones, aldehydes, esters, epoxides and C-X bonds Br LiEt 3 B Br LiEt 3 B LA 73% LiEt 3 B 100% C- 423 Course on rganic Synthesis; Course Instructor: Krishna P. Kaliappan 37

38 eduction Boron Based eagents Comparison Between Borohydride and Boranes Borohydrides Negatively charged Nucleophilic Valence shell of boron completed octet ydride transfer occurs intermolecularly Boranes Neutral Electrophilic Boron contains six electrons and a vacant p-orbital ydride transfer occurs via a Lewis acid-base complex C- 423 Course on rganic Synthesis; Course Instructor: Krishna P. Kaliappan 38

39 eduction Aluminum-based reagents Ø LiAl 4 Ø Li( t Bu) 3 Al Ø ed-al Ø Al 3 Ø DIBAL- Lithium aluminum hydride (LiAl 4 ) Very powerful reducing reagent Available as either powder or pallet Used as a suspension in ether or TF eacts violently with water, alcohol educes carbonyl, carboxylic acid & ester educes nitrile, amide & aryl nitro group to amine educes acetylene to olefin educes C-X bond, opens epoxide C- 423 Course on rganic Synthesis; Course Instructor: Krishna P. Kaliappan 39

40 eduction Mechanism: Aluminum-based reagents Li Al ' ' Li C Al 3 ' ' ' Li Al N ' ' C 4 N 2 ' C ' ' C 2 N 2 N 2 C 3 N C 2 N 2 C N C 2 N 2 C- 423 Course on rganic Synthesis; Course Instructor: Krishna P. Kaliappan 40

41 eduction Alkyl halides: eduction of alkyl halides go via radical mechanism This is proved by- Aluminum-based reagents X e X X + X + e LA I 81% Alkynes: It is complementary to that of partial hydrogenation 2 /Pd CaC 3 LA C- 423 Course on rganic Synthesis; Course Instructor: Krishna P. Kaliappan 41

42 Epoxides: eduction Aluminum-based reagents eduction LA LA Axial attack LA L-Selectride 93 7 C 2 Me C 2 Me LA C- 423 Course on rganic Synthesis; Course Instructor: Krishna P. Kaliappan 42

43 eduction Aluminum-based reagents C C 2 EASY C C CCl C 2 Lactone Diol Epoxide Alcohol Ester Alcohol Carboxylic acid Alcohol Carboxylate Salt Alcohol Amide Amine Nitrile Amine DIFFICULT C- 423 Course on rganic Synthesis; Course Instructor: Krishna P. Kaliappan 43

44 eduction Aluminum-based reagents Alane (Al 3 ) Preparation: AlCl 3 + LA Al 3 + 3LiCl It is inert to olefin & nitro group Br Me Al 3 Br Ph LA Ph Al 3 1,2- selective Ph C- 423 Course on rganic Synthesis; Course Instructor: Krishna P. Kaliappan 44

45 eduction Aluminum-based reagents Diisobutylaluminium ydride (DIBAL-) Al ighly pyrophoric Al(i-Bu) 2 DIBAL- Work up CEt DIBAL- C 2 Under carefully controlled conditions, will partially reduce an ester to an aldehyde C 2 Me C Me Al If complex is Unstable If complex is Stable Fast C C 2 C C- 423 Course on rganic Synthesis; Course Instructor: Krishna P. Kaliappan 45

46 eduction Aluminum-based reagents Direct conversion of acids to aldehydes: TMSCl DIBAL- Et 3 N TMS DCM, -78 o C Acid chloride to aldehyde using Weinreb s amide: Cl N Me Me N Me Me Weinreb's amide DIBAL- MgBr N Me Al Me C C- 423 Course on rganic Synthesis; Course Instructor: Krishna P. Kaliappan 46

47 eduction Aluminum-based reagents Meerwein Pondorff - Verley eduction Al( i Pr) 3 is the reagent Isopropanol is the hydride donor By-product is acetone everse process is known as ppenauer oxidation ' Al( i Pr) 3 i Pr ' Al i Pr i Pr ' Al i Pr i Pr ' C N 2 C N 2 Br Br C- 423 Course on rganic Synthesis; Course Instructor: Krishna P. Kaliappan 47

48 eduction Aluminum-based reagents Tris-(tert-butoxy) lithium aluminium hydride [LiAl( t Bu) 3 ] Preparation: LiAl t Bu LiAl( t Bu) Less reactive than LA Partial reduction is possible Alternative to osenmund reduction Cl Li( t Bu) 3 Al 2 N 2 N Cl Li( t Bu) 3 Al C 2 Cl Me N Me Pyridine -30 o C N Me Me Li( t Bu) 3 Al CuI (cat.) -78 o C C- 423 Course on rganic Synthesis; Course Instructor: Krishna P. Kaliappan 48

49 eduction Aluminum-based reagents Sodium bis(2-methoxyethoxy)aluminium hydride (ed-al) Me Me Na + Al educes lactones in presence of bulky ester ed Al C 2 t Bu C 2 t Bu pens epoxy alcohols through chelation Me Na + Me DIBAL- ed-al Al 49 C- 423 Course on rganic Synthesis; Course Instructor: Krishna P. Kaliappan

50 eduction In case of ed-al: Aluminum-based reagents Me Na + Al Me Al ' ' Na + ydrolysis In case of DIBAL-: Al Al Al ydrolysis C- 423 Course on rganic Synthesis; Course Instructor: Krishna P. Kaliappan 50

51 eduction Aluminum-based reagents Sharpless asymmetric epoxidation ed - Al Ph Ph Ph V(acac) 2 t-bu DIBAL - Ph Ph Bn Bn Bn ed - Al 150 : 1 DIBAL - 1 : 13 C- 423 Course on rganic Synthesis; Course Instructor: Krishna P. Kaliappan 51

52 eduction Free adical eactions Tributyltin hydride (TBT) Used to reduce alkyl halides Usual hydrogen donor is tributyltin hydride X TBT AIBN Δ C 3 Mechanism: NC N N CN Δ 2 N 2 Bu 3 Sn CN CN Bu 3 Sn Bu 3 Sn X Bu 3 Sn Bu 3 Sn C- 423 Course on rganic Synthesis; Course Instructor: Krishna P. Kaliappan 52

53 eduction Free adical eactions Barton- McCombie eaction: Na, CS 2 MeI MeS S n-bu 3 Sn AIBN PhC 3 S SMe SnBu 3 SnBu Bu 3 3 Sn S SMe TBT AIBN SnBu 3 1. Na/ CS 2 MeI 2. TBT C- 423 Course on rganic Synthesis; Course Instructor: Krishna P. Kaliappan 53

54 Thiocarbonate Modification: eduction Free adical eactions Ph S Cl S TBT AIBN Py, DMAP Ph PhC 3 adical Decarboxylation: (CCl) 2 N N S TBT AIBN S C- 423 Course on rganic Synthesis; Course Instructor: Krishna P. Kaliappan 54

55 eduction of Nitroalkanes: eduction Free adical eactions TBT AIBN 2 N Toluene Tandem eaction: 2 N AIBN TBT Toluene Δ C- 423 Course on rganic Synthesis; Course Instructor: Krishna P. Kaliappan 55

56 eduction Free adical eactions adical Cyclization eaction: Br AIBN TBT Br TBT, AIBN Toluene, reflux X nbu 3 Sn, AIBN Toluene, reflux 5-exo-trig C- 423 Course on rganic Synthesis; Course Instructor: Krishna P. Kaliappan 56

57 eduction Baldwin s ule Exo, Endo Dig, Trig, Tet Diagonal Trigonal Tetrahedral n-exo-trig n-endo-trig n = ring size π e - outside - exo π e - inside - endo exo-trig exo-dig C- 423 Course on rganic Synthesis; Course Instructor: Krishna P. Kaliappan 57

58 eduction Baldwin s ule X + X C 3 C 3 X C 3 X C 3 X C- 423 Course on rganic Synthesis; Course Instructor: Krishna P. Kaliappan 58

59 eduction Silane eagents Most commonly used silane reagents are Et 3 Si, i-pr 3 Si ydrosilylation: Et 3 Si 3 + (Ph 3 P) 3 hcl SiEt 3 eduction f Lactol Ethers: Me BF 3.Et 2 Et 3 Si C- 423 Course on rganic Synthesis; Course Instructor: Krishna P. Kaliappan 59

60 eduction Dissolving Metal eduction Birch eduction M A M A Li, Na, K, Ca, in Liquid ammonia, Et 2 N, EtN 2,, 2 Partial eduction f Aromatic ings: e e C- 423 Course on rganic Synthesis; Course Instructor: Krishna P. Kaliappan 60

61 eduction Dissolving Metal eduction Electron Donating Substituents: Me Me Me Me Me Li/ N 3 1e + 1e C 3 C 3 Ca N 2 Electron Withdrawing Substituents: C 2 Na/ N 3 C 2 1e C 2 1e C- 423 Course on rganic Synthesis; Course Instructor: Krishna P. Kaliappan 61

62 eduction Dissolving Metal eduction Both Electron Donating And Electron Withdrawing Substituents: C 2 Me Na C 2 Me 3 C 2 - C 2 Liq N 3 C 2 C 2 Na/liq. N 3 Me Me C 2 C 2 Na/liq. N 3 Me Me C- 423 Course on rganic Synthesis; Course Instructor: Krishna P. Kaliappan 62

63 eduction Dissolving Metal eduction Ketones and nitro groups get reduced keeping esters and nitriles untouched (1) Li, Liq N 3 (1) Li, Liq N 3 (2) xalic acid Me (2) 3 + Li xalic acid Me Liq N 3 Me Me Me 3 C- 423 Course on rganic Synthesis; Course Instructor: Krishna P. Kaliappan 63

64 eduction Dissolving Metal eduction α,β-unsaturated compounds are reduced in 1,4-fashion Li t Bu Li Liq N 3 Liq N 3 E E Li Li, Liq N 3 Li Br 1 eq 2 TMSCl TMS C- 423 Course on rganic Synthesis; Course Instructor: Krishna P. Kaliappan 64

65 eduction Dissolving Metal eduction (1) Li, Liq N 3 1 eq. t Bu (2) C 2 eduction of Alkynes: ' 1 e ' + ' 1 e ' + ' C- 423 Course on rganic Synthesis; Course Instructor: Krishna P. Kaliappan 65

66 eduction of Phosphates: eduction Dissolving Metal eduction Na Cl P(Et) 2 Li, EtN 2 P(Et) 2 t Bu 1 2 LDA Cl P(Et) P(Et)2 Li, EtN 2 t Bu 1 2 Asymmetric Birch eduction: N N Me (1) K, Liq N 3 (2) MeI Me C- 423 Course on rganic Synthesis; Course Instructor: Krishna P. Kaliappan 66

67 eduction Dissolving Metal eduction Mg in Me: X Mg Me X X = CN, C, CN 2 Me 2 C Mg Me Me 2 C C 2 Me Mg Me C 2 Me C- 423 Course on rganic Synthesis; Course Instructor: Krishna P. Kaliappan 67

68 eduction Dissolving Metal eduction Zn in Ac: Zn X Zn ZnX Ac Zn/MeI Br Zn/Ac Br Zn Br Zn, DMS Ac MeI C- 423 Course on rganic Synthesis; Course Instructor: Krishna P. Kaliappan 68

69 eduction Dissolving Metal eduction Zn in Ac: Zn/Ac Ac Zn/Ac Cl Zn/Ac C- 423 Course on rganic Synthesis; Course Instructor: Krishna P. Kaliappan 69

70 eduction Diimide eduction N NaC CNa N C 3 C N C C N - 2C 2 N N Syn addition N 2 N 2 2 C- 423 Course on rganic Synthesis; Course Instructor: Krishna P. Kaliappan 70

71 eduction Diimide eduction N 2 2 C 2 Me C 2 Me N 2 N 2 S hν N N N N CS C S N N hν, 16 h C- 423 Course on rganic Synthesis; Course Instructor: Krishna P. Kaliappan 71