Nitrile Oxides, Nitrones, and Nitronates in Organic Synthesis : Novel ...

REACTIONS OF DIPOLAR 1,3-CYCLOADDITION ([3 + 2] CYCLOADDITION) 299
Table 2.16 1,3-Dipolar cycloaddition of norbornadiene-tethered nitrones
Entry Starting aldehyde Cycloadduct a,b Yield d (%)
1
2
3
4
5
6
7
O
O
O
O
O
O
O
O
O
O
O
O
H O Me
N
H
O
O Me
N
H O Me
N
H
H
O
O
O Me
N
O
O Me
N
H O
c
Me
N
H O Me
N
a Reaction conditions: MeNHOH HCl (1.2–2 eq.), pyridine (3–5 eq.), 4 Å molecular
sieves, toluene, r.t., 12–24 h then 60°C to 90 °C 12–24 h.
b Except in entry 6, the cycloadducts shown were the only regio- and stereo- isomers
isolated in the cycloadditions.
c An inseparable mixture of three isomers was obtained.
d Isolated yields after column chromatography.
O
O
O
51
19
71
60
47
52
43