Exam Red. Flashcards
LAH (lithium aluminiumhydride)
Powerful, non selective, moisture sensitive
Work up Rochelle’s salt or can use EA.
-78 oC, ether or THF
Imine, amide -> amine
Acid halide, aldehyde, ester, carboxylate -> alcohol
LiBH4
Ester, lactone -> alcohol
Carboxylate ->X
0 oC, Ether > TFH > 2-propanol
Store protected from moisture
BH3.L
COOH -> -CH2OH Ester, lactone, amide, halide -> X Aldehyde, ketone, alkene -> OH In THF or Me2S 0-25 oC Generate diborane in situ by using NaBH4/BF3.Et2O
DIBAL
Ester -> CHO Lactone -> lactol Nitrile -> CHO -78 oC, ether, or Toluene or DCM Weinreb amide to aldehyde.****
LTEAH (Lithium triethoxyaluminumhydride)
Amide ->Aldehyde
LAH + 3 EtOH -> LTEAH + 3H2
1. Ether, THF, hexane
2. H+
Acid chloride -> Aldehyde
- Rosemund: from COOH
1. SOCl2
2. H2, Pd/BaSO4 - STBA (Sodium tri-tert-butoxyaluminiumhydride)
STBA, diglyme, THF, -78 oC
Aldehyde, ketone -> alkane
- Deoxygenation of Tosylhydrazone
1. TsNHNH2, EtOH
2. 90 oC, Na(CN)BH3, MeOH (may need acid, ZnCl2)
2. Wolff-Kishner Red.
2.1. diethylene glycol, Na, H2NNH2, 210 oC
2.2. TBSH (N-tert-butyldimethylsilylhydrazone), Sc(OTf)3; t-BuOK, t-BuOH, DMSO, 23-100 oC, 24h.
3. Thioacetal (thioketal) react with (Raney Ni, H2)
4. Clemmensen Red.
40% aqueous HCl, Zn(Hg)
NaBH4
Aldehyde, ketone -> alcohol
At 25oC, ester, epoxide, lactone, carboxylate, nitro, nitrile -> X
25 oC, EtOH or MeOH.
Luche reduction
NaBH4, CeCl3 allylic alcohol
MeCN, or MeOH
Ionic halogenation ***
Proton donor combination with hydride donor
Organisilane + TFA
Reduction of carbonium ion generated by protonation of ketone, alkene, or a lactol.
Samarium iodide (SmI2)
Aldehyde, ketone -> alcohol Alkyl halide -> ???? Carboxylate, ester -> X SmI2, THF/ H2O or iPrOH. Meerwein-Ponndorf-Verley red.
Reductive amination
C=O + Anime (mild acid) then Na(CN)BH3, Sn(OTf)3
4 A MS, DCE, 0 oC.
Or MeOH
Barton Deoxygenation **
R-OH -> thiocarbonate -> RH
- 1,1’-thiocarbonyl-imidazole, DMAP, DCM
- AIBN, Bu3SnH, toluene, 75 oC
In Tin-free Barton-type reduction
B(CH3)3, H2O\Benzene, 23 oC
Diazene-Mediated deoxygenation ????
R-OH->R-N(NH2)SO2Ar->RH 1. PPh3, DEAD, NBSH (Mitsunobu displacement) THF, -30 oC NBSH (o-nitrobenzenesulfonylhydrazine) DEAD (Diethyl azodicarboxylate)
** Add alkyllithium to N-t-butyldimethylsilyl aldehyde tosylate hydrazine at -78 oC followed by acid.????
Reduction of alkyl tosylate
LAH is not very good.
use LiEt3BH (super hydride) give higher yield!
toluene, 90 oC
or THF, H2O2, NaOH, MeOH
Radical dehalogenation
Reduction of Chloride need hard condition
when Fluoride is not work in pratice.
Formed radical 3o > 2o > 1o (stability)
Bu3SnH, AIBN, THF, PhBr 80 oC
AIBN (azobisisobutyronitrile) –> 2-cyanoprop-2-yl radical when heat or hv
Barton decarboxylation
R-COOH -> RCOCl
RCOCl + N-hydroxypyridine-2-thione -> Barton ester
–> Then radical (t-BuSH, toluene, 80 oC/// or Bu3SnH)
Diol -> Olefin
Corey-Winter Olefination Diol + thiocarbonyldiimidazole -> thiocarbonate Can use alternative approach: 1) diol + Cl2C=S, DMAP 2) decomposition P agent
Eastwood Deoxygenation
Diol + HC(OEt)3, AcOH -> ortho ester heat –> Decompose
Decompose bezilidene acetal
LDA, t-BuOK, THF, heat.
Stryker reduction
