Aziridine-allylsilane

When the related aziridine 195 was used containing one less carbon in the tether, an unusual cyclization occurred which corresponds to a formal [3+2] aziridine allylsilane cycloaddition to give the bicyclic pyrrolidine 196. This substrate was used for the preparation of other fused ring systems (Scheme 53) <1999T8025>. 

The asymmetric total synthesis of rauwolfia alkaloids (-)-yohimbane and (-)-alloyohimbane was carried out by S.C. Bergmeier et al. by utilizing a novei aziridine-allylsilane cyclization and the Bischler-Napieralski isoquinoline synthesis as key steps.These alkaloids have a characteristic pentacyclic ring framework and exhibit a wide range of interesting biological activities such as antihypertensive and antipsychotic properties. 

Bergmeier, S. C., Seth, P. P. Aziridine-Allylsilane-Mediated Total Synthesis of (-)-Yohimbane. J, Org, Chem, 1999, 64, 3237-3243. 

Oshima and coworkers reported the preparation of allylsilanes such as 148 by ringopening reactions of three-membered rings such as aziridines 147 with silylalu-minium reagents as shown in Scheme 2.38 [58]. 

The ring opening of an aziridine can also occur in an intramolecular fashion, as observed in the formal [3+2] azitidine-allylsilane cycloaddition reaction of 142. These substrates were used for the preparation of both 5-5 and 6-5 fused ring systems <99T8025>. 

Reaction with Further Electrophiles of Group IVA (Sl,Ge,Sn). IV-Silylated aziridines can be prepared from ethyleneimine by amination of chlorosilanes in the presence of an HC1 acceptor, by dehydrocondensation with an organosilicon hydride or by cleavage of a silicon—carbon bond in 2-furyl-, 2-thienyl-, benzyl-, or allylsilanes in the presence of an alkali metal catalyst (262—266). N-Silylated aziridines can react with carboxylic anhydrides to give acylated aziridines, eg, A/-acetylaziridine [460-07-1] in high yields (267). At high temperatures, A/-silylaziridines can be dimerized to piperazines (268). Aldehydes can be inserted... 

Lewis acid catalyzed intramolecular coupling of allylsilanes with aziridines serves as a useful route for the synthesis of carbocycles having the y-amino olefin unit 104 (equation 80)149. However, this reaction does not occur in an intermolecular manner. 

Allylsilanes act as good acceptors of nitrones and oxyallyl cations. The 1,3-dipole species arising from electronically activated cyclopropanes can be trapped by allylsilanes.203 204 2043 Epoxides as well as aziridines act as 1,3-dipole precursors for inter- and intramolecular [3 + 2]-cycloadditions with allylsilanes.205 2053 206 2063... 

The 1,3-dipole species arising from electronically activated cyclopropanes and a Lewis acid can be trapped by allylsilanes [505, 506]. Epoxides [507] and aziridines [508] also serve as 1,3-dipole precursors to react with allylsilanes inter- or intramolecularly, affording 2-silylmefhyl-THF derivatives and pyrrolidines, respectively (Scheme 10.189). 

Cyclic mutation. Intramolecular allylation leads to formation of a carbocycle in exchange for an aziridine when the heterocycle contains an allylsilane moiety in a side, hain. The transformation is initiated by BF OEti. ... 

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