Page 612 - Advanced Organic Chemistry Part B - Reactions & Synthesis

586 Scheme 6.18. Carbon-Carbon Bond Formation via [2,3]-Sigmatropic Rearrangements of
Sulfonium and Ammonium Ylides
CHAPTER 6
A. Sulfonium ylides
Concerted CH
Cycloadditions, 1 a 3 SCH 3
2
Unimolecular (CH ) C CHCH + S CO C H Na CO 3
Rearrangements, and 3 2 2 CH 2 2 2 5 (CH ) CCHCO C H
2 2 5
3 2
Thermal Eliminations
CH CH 2 91%
2 b +
K OC(CH )
3 3
+ H
S S
–40°C 85%
CH 3 H
H
3 c
CH
CH CO 2 CH 3
3
CH 3 DBU 3
H O 2 CCH 3
CH 3
H + 20°C C H O C S CH 3
S 2 5 2
CH 3 40%
CH CO C H
2
2 2 5
PhS CO C H
4 d 2 2 5
CO C H CH
CH 2 2 2 5 2
S + KOt Bu
N Ph N
H
C H C 2 5 70%
2 5
B. Ammonium ylides
5 e
H DBU
+
N CH CH 2 N
20°C
PhCH 2 CH CO C H CO C H
2
2 2 5
90%
PhCH 2 2 2 5
6 f
N
+
N + –
K O-t -Bu CHCN
(CH ) C CHCH 2 CH 2 CN (CH 3 ) 3 C
3 3
CH CH 2
94%
7 g
CH 3 CH CH 3
3
CH 3 CH 3 KOC H PhCH O CO C H
2 2 5
2 5
N + CO C H 2
2 2 5
CH 3 N(CH )
3 2
OCH 2 Ph
43%
(Continued)