Alkynes Reaction Acidity Synthesis. Complex of Acetylene Bonds.
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Transcript of Alkynes Reaction Acidity Synthesis. Complex of Acetylene Bonds.
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Alkynes
Reaction
Acidity
Synthesis
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Complex of Acetylene
Bonds
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Hydrocarbon Comparison
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Alkyne Nomenclature
HC CCH2CH2CH3
1-pentyne 4-decyne
CH2C C CH3
3-(2-butynyl)cyclohexene 5-phenyl-1-hepten-6-yne
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Enes with Ynes
chain numbered from end closest to -bond
1 57
7,8-dimethyl-5(E),7(Z)-decadien-1-yne
tie goes to the alkene
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Endiyne Antitumor Agents
HO cycloaromatizationHO
.
.
HO H abstraction
diradical
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NH
O
O
OH
OH OH
CO2H
OCH3
CH3
O
Dynemycin AAntitumor antibiotic
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O
OO
O
O
CH3
OCH3HO
O
OO
NHCH3
HO
HO
CH3
base:
O
CH3
OCH3OO
OO
NHCH3
HO
HO
CH3
OO
O
OHNCS-chrom
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NCS-chrom
O
OO
O
O
CH3
OCH3O
O
OO
NHCH3
HO
HO
CH3
H
base:
OH
OO
O
O
CH3
OCH3OO
OO
NHCH3
HO
HO
CH3
H-base
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OH
OO
O
O
CH3
OCH3OO
OO
NHCH3
HO
HO
CH3
O
CH3
OCH3OO
OO
NHCH3
HO
HO
CH3
OO
O
OH
.
.Diradical intermediate undergoes
H atom transfer with ribose backbone in DNA
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Catalytic Hydrogenation
75 psi
H2 - 1%Pt on C
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Lindlar’s Catalyst
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H2 on a Poisoned Catalyst Prevents Over-Reduction
cis Alkenes
5-decyne
H2 / Pd on BaSO4
quinolineLindlar's catalyst H H
H2, 1%Pt on C
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Dissolved Lithium in NH3
trans Alkenes
trans more stable
H NH2
C=CCH3
CH3
HLiCH3
H
C=CCH3
H
H
H N
CH3C=CCH3
LiHCH3
H CH3
C=C-78oC
Li in NH3(l)CCH3CH3C
.. .
.
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Addition of HX
CH3CH2C CHHBr
CH2CH3CH2C
BrHBr
CH3CH2CCH3
Br
Br
CH3CH2C=CH2
vinyl carbocationsp hybridized
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Br2 Addition
C CH Br2C C
HBr
Br
C
Br
Br
C
Br
Br
H
Br2
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Oxymercuration HydrationMarkovnikov
CH3CH2C CHHgSO4, H2SO4
H2OCH3CH2C=CH2
OH
an enol
CH3CH2CCH3
O
a ketone
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Enol – Keto TautomerizationIntermolecular
3
OH
CH
HCH3CH2C
OH
CH
HCH3CH2C
OH
CH
HCH3CH2C
CH3CH2CCH3
O
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Oxymercuration Mechanism
enol
SO42-SO42-
H3O+
tautomerization
OH
CH
HCH3CH2C
H2O
CH3CH2C CHg
HOH
O
CH3CH2CCH3
H2OO
HH
CHg
HCH3CH2C
vinyl carbocation
Hg+2
CH3CH2C CHg
H
HgSO4, H2SO4(aq)CHCH3CH2C
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Hydroboration HydrationAnti-Markovnikov
2) H2O2, NaOH
1) disiamyl borane
O
CH3CH2CH2CH
CHCH3CH2C
an enol
OH
CH3CH2CH=CH2
an aldehyde(sia)2BH
B
H
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Hydroboration Mechanism
CH3CH2C CH CH3CH2CH2CH
O1) disiamyl borane
2) H2O2, NaOH
B
H
(sia)2BH
CH3CH2C
H
CH
B(sia)2H2O2, NaOH
CH3CH2CH=CH2
OH
enol
tautomerization
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Draw the Products
C CH1) disiamylborane, THF
2) H2O2, NaOH
HgSO4, H2SO4 (aq)
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C CH1) disiamylborane, THF
2) H2O2, NaOH
HgSO4, H2SO4 (aq)
CH2CH
CCH3
O
O
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Ozonolysis
CH3CH2C CCH3O3
H2O CH3CH2C=O
OH
O=CCH3
OH
+
2 carboxylic acids
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Acidity of Terminal Alkynes
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Acetylide Formation
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Alkylation of Acetylide IonsHomologations using SN2 rxn
CH3CH2CH2C C HNaNH2
in NH3(l)-78 C
o
CH3CH2CH2C C Na
CBr
H
HH
CH3CH2CH2C CCH3
SN2NH2
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Multi-step Syntheses
HC CH Br?
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Retrosynthetic AnalysisBegin with the Product
HC CH Br?
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Fill in the Reagents
HC CH Br?
1) NaNH2, NH3
2) Br
H2, Lindlar's cat.
HBrROOR, h
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How Many Steps?
CHHCCH2CH(CH3)2
H
H
CH3
?
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5 Steps
CHHCCH2CH(CH3)2
H
H
CH3
1) NaNH2, NH3
2) CH3I
3) NaNH2, NH3
4) (CH3)2CHCH2Br5) Li, NH3
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An unknown compound (A) has a formula of C11H14. Treatment of A with H2/Pd-carbon gives B
(C11H20). Treatment of A with H2 on a Lindlar
catalyst gives C (C11H16). Ozonolysis of C followed
by workup with Zn, HOAc affords formaldehyde and the tricarbonyl compound shown below.
O
+ HCHCH
O
O
O
H
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Schematic of the Problem
2) Zn, HOAc
1) O3
H2 / Lindlar's cat.
C11H20C11H14
BH2 / Pd on carbon
A
CC11H16
CH
O
O
O
H
+ HCH
OC
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• An initial approach to this problem is to determine the number of degrees of unsaturation in each of the molecules A, B, and C.
• When A (C11H14, 5o unsat.) is hydrogrenated, B (C11H20, 2
o unsat.) is formed. That means that 3 bonds reacted (3 mol. equivalents) to form B.
• When A is treated with H2 over a Lindlar (poisoned) catalyst, 1 mol equiv. of H2 reacts. Since this reaction is specific for the reduction of alkynes to alkenes, 2 of the 3 bonds in A are in the form of a triple bond. The remaining bond must be an alkene.
• We have accounted for three of the five degrees of unsaturation in A, therefore the other two must be rings since they do not react with H2.
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Propose Structures for A, B, and C
H2, Pd/C
A B
H2
Lindlar's cat.
1) O3
2) Zn, HOAc(aq)
OO O
H
CO
CH2
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Nucleophilic addition to Carbonyl Compounds
C
O
CH3CH3
CH3CH2C C
C
O
CH3CH3
CCH3CH2C
CH3CH2C C
CH3 CH3
OH
C
H3O+
H
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Synthesis Problem
C CH
H
CH3CH2
CHCH2CH3
OH
target molecule
from acetylene and any
2- or 3-carbon reagents
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Retrosynthetic Analysisfrom acetylene
C CH
H
CH3CH2
CHCH2CH3
OH
target moleculeCH3CH2X
HC CHHCCH2CH3
O