Page 174 - Advanced Organic Chemistry Part B - Reactions & Synthesis

146 acyliminium ions. 205 N-Acyliminium ions can also be obtained by oxidative decar-
boxylation of N-acyl- -amino acids such as N-acyl proline derivatives. 206
CHAPTER 2
Reactions of Carbon
Nucleophiles with H PhI(OAc) , I 2
2
Carbonyl Compounds N CO 2 N OCH 3
CH OH
CH 3 CO CH
CO 2 3 2 3
Acyliminium ions are sufficiently electrophilic to react with enolate equivalents
such as silyl enol ethers 207 and isopropenyl acetate. 208

O CCH 3 OTMS (CH ) SiO SCF 3 CH CPh
2
2
3 3
3
+ CH C
N 2 N O
O Ph O
TMS H 89%
Acyliminium ions can be used in enantioselective additions with enolates having chiral
auxiliaries, such as N-acyloxazolidinones or N-acylthiazolidinethiones.
Cl
Cl Cl H O O
Ti
O O N O
N OC 2 5 + N
H
CH 3
CO C(CH ) N O (CH ) CO C CH 3
3 3
2
3 3
2
PhCH 2
PhCH 2
Ref. 209
Sn CH 3
CCH O O
O 2 3 S S
+ CH 3 N N
N S O N S
O TMS H

Ref. 210

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206
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208
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210
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