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

REFERENCES 727
Due to the silylation of AN, the latter can be considered as promising precursors
of various nitroso acetals (primarily of ene nitroso acetals), conjugated
en-oximes, α-nitrosoalkenes, and some other products. Convenient alternative
methods for the synthesis of most of the above mentioned compounds are lacking.
All of these facts substantially extend the possibilities of using AN in organic
synthesis. There are prerequisites for the development of new strategies for the
organic synthesis involving silylation of AN as the key step. Of course, these
aims will be realized in future.
But now, a strategy, used for the synthesis of derivative (622) (lit. synthesis
(622) see in Ref. 555), which is the most efÞcient analog of the commercial
drug rolipram with a broad spectrum of action (in particular, anti-inßammatory,
antidepressant, neuroprotective, and immunodepressing effects), is presented in
Scheme 3.286. (The principle action of rolipram is based on selective inhibition of
adenosine monophosphate (AMP)-speciÞc phosphodiesterase.) Derivative (622)
is almost 10 times more efÞcient than rolipram, but the biological activity of
(622) was determined only for the racemate (555).
An original approach to the synthesis of (622) from nitroethane was silylation
of the key step (618→619) (556). This approach involves a smaller number of
steps and gives the products in a higher yield. The obvious advantage of this
approach is that it can be performed enantioselectively.
The synthesis nitroethane→(622) provides a good example of the potential of
using silylation of AN in organic synthesis.
REFERENCES
1. (a) Hantzsch A, Schultze OW. Chem. Ber. 1896; 29: 699;
(b) Konovalov MI. Chem. Ber. 1896; 29: 2193.
2. Torssell KBG. NitrileOxides, Nitrones, and Nitronates in Organic Synthesis, VCH
Publishers, New York, 95–101, 1988.
3. Denmark SE, Cottell JJ. The Chemistry of Heterocyclic Compounds, Vol. 59: Synthetic
Applications of 1,3-Dipolar Cycloaddition Chemistry Toward Heterocycles and
Natural Products, John Wiley & Sons, 130–133, 2002.
4. Torssell KBG. NitrileOxides, Nitrones, and Nitronates in Organic Synthesis, VCH
Publishers, New York, 105, 1988.
5. Takayama H. Chem. Pharm. Bull. 1978; 26: 2575–2578.
6. Kurfuerst A, Kuthan J. Collection 1983; 48: 1718–1728.
7. Sato H. Chem. Lett. 1975: 965–966.
8. Bodina RI, Lipina ES, Perekalin VV. J. Org. Chem. USSR 1976; 12: 2039–2043
(2095–2098 russ.).
9. Tartakovsky VA, Chlenov IE, Lagodzinskaja GV, Novikov SS. Dokl. Chem. Russ.
1965; 161: 257–260 (136–139 russ.).
10. Falck JR, Yu J. Tetrahedron Lett. 1992; 33: 6723–6726.
11. Mitsunobu O, Yoshida N. Tetrahedron Lett. 1981; 22: 2295–2296.
12. Thurston JT, Shriner RL. J. Org. Chem. 1937; 2: 183;
Thurston JT, Shriner RL. J. Org. Chem. 1937; 2: 191.