ACILIRANJE ENOLAT - ANIONA - pmf.unsa.ba za organsku hemiju i biohemiju... · formirati enolat i...
Transcript of ACILIRANJE ENOLAT - ANIONA - pmf.unsa.ba za organsku hemiju i biohemiju... · formirati enolat i...
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Claisenova kondenzacija
• β-keto esteri se pripremaju pomoću
Claisen-ove kondenzacije.
• Koriste se etil esteri sa Na-etoksidom kao
bazom
2RCH2RCH22COR'COR'
OO1. 1. NaORNaOR''
2. H2. H33OO++
++ R'OHR'OH
OO OO
RCHRCH22CCHCOR'CCHCOR'
RR
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Primjer:
• Produkt iz etil acetata se naziva etilacetoacetat
ili acetoacetatni ester
2CH2CH33COCHCOCH22CHCH33
OO1. NaOCH1. NaOCH22CHCH33
2. H2. H33OO++
OO OO
CHCH33CCHCCH22COCHCOCH22CHCH33
(75%)(75%)
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Korak 1Korak 1::
CHCH33CHCH22 OO––••••••••
••••
••••
COCHCOCH22CHCH33
OO
CHCH22HH
••••
––••••
••••
COCHCOCH22CHCH33
OO
CHCH22CHCH33CHCH22 OO••••
••••HH
••••
Mehanizam:
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Mehanizam
Korak Korak 1:1:
––••••
••••
COCHCOCH22CHCH33
OO
CHCH22
••••
––••••
COCHCOCH22CHCH33
OO
CHCH22
••••
••••
• Anion koji nastaje stabilizira se delokalizacijom elektrona (rezonancijom); to je enolat estera
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Mehanizam
KorakKorak 2:2:
––••••
••••
COCHCOCH22CHCH33
OO
CHCH22
••••
CHCH33COCHCOCH22CHCH33
OO ••••••••
CHCH33CC
––OO••••••••••
••••••
COCHCOCH22CHCH33
OO
CHCH22
••••
OCHOCH22CHCH33••••••••
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Mehanizam
KorakKorak 3:3:
CHCH33CC
––OO••••••••••
••••••
COCHCOCH22CHCH33
OO
CHCH22
••••
OCHOCH22CHCH33••••••••
––OCHOCH22CHCH33••••••••••••
CHCH33CC
OO••••••••
••••
COCHCOCH22CHCH33
OO
CHCH22
••••
++
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Etoksid privlači proton iz CH2
grupe dajući stabilizirani anion:
––OCHOCH22CHCH33••••••••••••
CHCH33CC
OO••••••••
••••
COCHCOCH22CHCH33
OO
CHCH22
••••
++
KorakKorak 4:4:
++ OCHOCH22CHCH33••••
••••HH
––
••••
COCHCOCH22CHCH33
OO ••••
CHCH33CC
OO••••••••
CHCH••••
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++
KorakKorak 5:5:
––
••••
COCHCOCH22CHCH33
OO
CHCH33CC
OO••••••••
CHCH••••
++OOHH ••••
HH
HH
OO
HH
••••
HH
••••CHCH33CC
OO••••••••
••••
COCHCOCH22CHCH33
OO
CHCH
••••
HH
+
Reakciona smjesa se zakiseli i to prevodi anion u
izolirani produkt, etil acetoacetat:
OO
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Primjer 2:
• Reakcija uključuje
formiranje veze
izmeñu α-karbonovog
atoma jedne molekule
propanoata i karbona
karbonilne grupe
druge molekule.
2CH2CH33CHCH22COCHCOCH22CHCH33
OO
1. NaOCH1. NaOCH22CHCH33
2. H2. H33OO++
(81%)(81%)
OO OO
CHCH33CHCH22CCHCOCHCCHCOCH22CHCH33
CHCH33
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CHCH33CHCH22OCCHOCCH22CHCH22CHCH22CHCH22COCHCOCH22CHCH33
OO OO
1. NaOCH1. NaOCH22CHCH33
2. H2. H33OO++
Primjer
COCHCOCH22CHCH33
OO OO
(74(74--81%)81%)
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CHCH33CHCH22OCCHOCCH22CHCH22CHCH22CHCH22COCHCOCH22CHCH33
OO OO
NaOCHNaOCH22CHCH33
preko
CHCH33CHCH22OCCHOCCH22CHCH22CHCH22CHCOCHCHCOCH22CHCH33
OO OO
••••
––
••••••••
••••••••
••••••••
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CHCH33CHCH22OCCHOCCH22CHCH22CHCH22CHCOCHCHCOCH22CHCH33
OO OO
••••
––
••••••••
••••••••
CHCOCHCHCOCH22CHCH33
OO
––
••••••••
CHCH22HH22CC
HH22CC
CC
OO••••••••
••••CHCH33CHCH22OO
••••
••••
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CHCOCHCHCOCH22CHCH33
OO
––
••••••••
CHCH22HH22CC
HH22CC
CC
OO••••••••
••••CHCH33CHCH22OO
••••
••••
CHCH33CHCH22OO••••
••••••••––
••••••••
CHCOCHCHCOCH22CHCH33
OO
CHCH22HH22CC
HH22CC
CC
OO••••••••
++
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Mješovita Claisen-ova kondenzacija
• Kao i kod mješovite aldolne kondenzacije, mješovitu
Claisen- ovu kondenzaciju je najbolje izvoditi
kada reakciona smjesa sadrži jedno jedinjenje koje može
formirati enolat i jedno koje ne može (da se nebi stvarala
smjesa produkata).
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• Ovi tipovi estera ne mogu graditi enolate.
HCORHCOR
OO
ROCORROCOR
OO
ROCROC
OO
CORCOR
OO
CORCOR
OO
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Primjer
1. NaOCH1. NaOCH33
2. H2. H33OO++
(60%)(60%)
COCHCOCH33
OO
++ CHCH33CHCH22COCHCOCH33
OO
OO OO
CCHCOCHCCHCOCH33
CHCH33
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Primjer
1. 1. NaHNaH
2. H2. H33OO++
(60%)(60%)
++CHCH33CHCH22OCOCHOCOCH22CHCH33
OO
OO
OO
COCHCOCH22CHCH33
OO
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Primjer
1. NaOCH1. NaOCH22CHCH33
2. H2. H33OO++
(62(62--71%)71%)
COCHCOCH22CHCH33
OO
++
OO
CHCH33CC
OO
OO
CCHCCH22CC
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Sinteza ketona
•β-keto kiseline se lahko dekarboksiliraju
dajući ketone
++
OO
RCHRCH22CCHCCH22RR
OO OO
RCHRCH22CCHCOHCCHCOH
RR
COCO22
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Sinteza ketona
•β-keto kiseline se dobivaju hidrolizom β-
keto estera.
OO OO
RCHRCH22CCHCOR'CCHCOR'
RR
OO OO
RCHRCH22CCHCOHCCHCOH
RR
HH22OO++ R'OHR'OH
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Sinteza ketona
β-keto esteri mogu biti pripremljeni
Claisenovom kondenzacijom.
2RCH2RCH22COR'COR'
OO1. 1. NaORNaOR''
2. H2. H33OO++
++ R'OHR'OH
OO OO
RCHRCH22CCHCOR'CCHCOR'
RR
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Primjer
1. NaOCH1. NaOCH22CHCH33
2. H2. H33OO++
(80%)(80%)
2 CH2 CH33CHCH22CHCH22CHCH22COCHCOCH22CHCH33
OO
CHCH33CHCH22CHCH22CHCH22CCHCOCHCCHCOCH22CHCH33
OO OO
CHCH22CHCH22CHCH33
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Primjer
1. KOH, H1. KOH, H22O, 70O, 70--8080°°CC
2. H2. H33OO++
CHCH33CHCH22CHCH22CHCH22CCHCOCHCCHCOCH22CHCH33
OO OO
CHCH22CHCH22CHCH33
CHCH33CHCH22CHCH22CHCH22CCHCOHCCHCOH
OO OO
CHCH22CHCH22CHCH33