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78 Cards in this Set
- Front
- Back
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Factors controlling ring synthesis through cyclization |
Thermodynamics 5,6 favoured Kinetics eyring equation - delta h and s |
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For different ring sizes |
3: fast, S= favourable little preorganisation outweighs H ring strain 4: slower, S = less favourable as more ordered, H similar, harder to form 5: fastest gets smaller as well increasing across normal and medium S increases with increasing ring size 5-7 H constant 5-7 as relatively unstrained S increasing proportionately less as ring size increases medium H dominant as large transannular strain Large: S unfavourable - oligomerisation H no ring strain so unimportant Form large rings under high dilution Substrate dependent |
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Ring size 3,4,5 |
3 favourable entropy dominates 4 unfavorable 5 enthalpy dominates |
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3,4,5,6 |
3 unfavourable sp2 strain 5 favourable entropy and enthalpy |
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Baldwin's rules |
Approach at 180 for Max homo-lumo overlap - need correct orbital alignment Baldwin's original rules and changes Table Exo tet and trig all allowed Endo tet and trig disallowed (except 6 endo-trig) All exo allowed by new rules |
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Cyclization |
Attack at oxygen because poor orbital overlap for carbon attack 5-enolendo-exo-tet disfavoured 5-exo-tet favoured |
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Cyclization |
Attack from carbon |
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Baldwin's rules for enolates |
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What happens |
6 endo tet disafvoured |
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What happens |
6 exo tet favoured |
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5 factors controlling ring synthesis through cyclization |
Thermodynamics Kinetics Stereoeletronic effects Thorpe Ingold effect Macrocyclic conformational control: templating/preorganization effects |
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What happens |
Radical cyclizations |
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Reaction and reactants |
Bu3sn and trace AIBN |
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5 endo trig disfavoured 6 endo trig favoured |
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What happened |
Nah naome no reaction since 5 endo trig disfavoured Cat tsoh c6h6 heat yes 5-exo trig favoured |
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Acetal formation |
5 endo trig favoured as p orbital being attacked |
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Explain x4 |
Thorpe-Ingold effect (A) lower H due to ground state bond angle compression (B) lower H due to ground state relief on commission (less sterics between Me groups) (C) lower S - reduced population of non reactive conformations (D) lower S - poor solvation of tertiary alcohols |
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Cyclization order |
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Make this |
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Make this |
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Synthesise this |
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Make this |
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Dieckmann don't forget h+ workup |
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Use reversibility of dieckmann |
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Robinson annelation = Michael and aldol |
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Synthesise this |
Robinson annelation |
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Synthesise |
Robinson ring annelation |
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Synthesize |
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5 exo trig |
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25 |
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What happens |
26 |
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27 |
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Carbene and carbenoid |
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30 |
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30 |
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Ozonolysis 31 |
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Go on do it P32 |
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P32 |
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P32 |
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Make this |
P32 |
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Make |
Nitrite oxide and alkyne |
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P35 |
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P36 |
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P36 |
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P36 |
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38 |
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Favorskii naoh |
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39 |
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39 |
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Ruzicka |
Notes p3 grossel |
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Make that |
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P3 grossel notes |
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P3 grossel |
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P3 grossel |
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Thorpe Ziegler then hydrolysis then decarboxylation p3/4 notes grossel |
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Thorpe Ziegler |
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Robinson ring annelation p4 grossel |
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P4 grossel |
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P4 grossel |
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P4 grossel |
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P4 grossel |
