L Le ev ve el l 2 2 – – C Ca as se e 2 24 4
R Re ea ar rr ra an ng ge em me en nt ts s o of f C Cy yc cl lo ob bu ut te en no on ne es s
K Ke ey y p po oi in nt t: : E El E El El E El E E e
le l le le le l lec ct tr t tr tr t tr t t o
ro r ro ro ro ro r roc cy cy cy yc y yc yc yc yc yc y y l li li li l li li l lic ic ic ic i i r ri ri ri r ri ri r rin i in in in i i g g c cl lo los su ur re re r re re re re r res s a
an nd d r ri ri ri r ri ri r rin i in in in i i g g o op op op pe en ni in i in in in i i g gs s s
gs
C C Li
Ph
O
OMe
OMe
MeO
C C Li
Ph
H
O
C
OMe
OMe
PhCH 2
O
OMe
OMe
H
Ph
1)
THF, -78
o C
2) Toluene,110
o C
THF, -78
o C
1)
R Re ea ar rr ra an ng ge em me en nt ts s o of f C Cy yc cl lo ob bu ut te en no on ne es s
Treatment of 1 with 1-lithio-3-phenyl-1-propyne in THF at –78°C, yields 3-alkynyl cyclobutenone 2 that after being refluxed in toluene gives naphthofuran derivative 3 in 45% yield (Scheme 24.1).
O
OMe
OMe
MeO
C C Li
Ph
O
OMe
OMe
Ph
O
C
OMe
OMe
PhCH 2
H
1
3
2
Toluene
110 o C
THF, -78 o C
Scheme 24.1