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

REACTIONS OF DIPOLAR 1,3-CYCLOADDITION ([3 + 2] CYCLOADDITION) 343
Sug N + Bn
O −
574 - 576
i
Sug CO2Me Sug
CO2Me Sug CO2Me Sug CO2Me + + +
Bn
N O
Bn
N O
Bn
N O
Bn
N O
577 a - 579 a 577 b - 579 b 577 c - 579 c 577 d - 579 d
ii
OH
ii
OH
Sug N O Sug N O Sug N O Sug N O
Bn
Bn
Bn
Bn
580 a - 582 a 580 b - 582 b 580 c - 582 c 580 d - 582 d
Sug N +
O
Bn
−
:
i. Methyl acrylate
ii. Zn/AcOH-H2O, 60°C, 5 h
O
OMe
O
Bn
N +
ii
OH
BnO
O O −
O
O
574 575
O
O
O
O
O
Scheme 2.264
O
576
Bn
N +
O −
Bn
N +
positions. This is caused mainly by electronic factors. The more electron-deÞcient
end of the dipolarophile adds to the nitrone oxygen atom. As illustrated in Scheme
2.265, all reactions gave cisand trans cycloadducts (587) to(594) (775).
Recently, an example of green chemistry in the formation of a nitrone in
aqueous medium, using a surfactant, was reported in 1,3-dipolar cycloadditions
to ethyl acrylate (776). The control of regioselectivity in this reaction favors the
formation of trans-5-substituted isoxazolidines.
O −
ii
OH