Propargyl aziridines

Propargylic aziridines were obtained in one step on reaction of this allenylzinc reagent with imines (Eq. 9.130) [108, 109]. 

The reactions of propargylic aziridines with a platinum catalyst in aqueous media led the cycloisomerization of aziridines 39 forming pyrroles 40 (Scheme 13) [45]. According to the proposed mechanism, the platinum coordinates with carbon-carbon triple bond that is followed by attack of the aziridine nitrogen on the alk5me forming a pyrrolyl-platinum species, which undergoes aromatization to form the final pyrrole products. 

Aziridines Bearing Alkyl, Aryl, Propargyl, and Vinyl Groups... 

The stereochemistry of the first step was ascertained by an X-ray analysis [8] of an isolated oxazaphospholidine 3 (R = Ph). The overall sequence from oxi-rane to aziridine takes place with an excellent retention of chiral integrity. As the stereochemistry of the oxirane esters is determined by the chiral inductor during the Sharpless epoxidation, both enantiomers of aziridine esters can be readily obtained by choosing the desired antipodal tartrate inductor during the epoxidation reaction. It is relevant to note that the required starting allylic alcohols are conveniently prepared by chain elongation of propargyl alcohol as a C3 synthon followed by an appropriate reduction of the triple bond, e. g., with lithium aluminum hydride [6b]. 

An application of copper-catalyzed propargylic etherification has been reported in the synthesis of ustiloxin D (Equation (63)).248 Here, a quaternary center was generated from the unprecedented reaction of a phenol with an ethynyl aziridine. 

D hooghe, M. Van Brabandt, W. De Kimpe, N. New Synthesis of Propargylic Amines from 2-(Bromomethyl)aziridines. Intermiediacy of 3-Bromoazetidinium Salts. /. Org. Chem. 2004, 69, 2703-2710. 

Chemla and Ferreira effected lithiozincation of TMS propargyl chloride to prepare chloroal-lenylzinc bromide reagents (Table 21)33. Subsequent reaction of these reagents with N-t-butyl-substituted sulfoximines yielded the related traws-sulfoxinyl aziridines, arising from internal displacement of the chloride substituent of the anti sulfinamide adduct. A transition state in which the f-BuSO group is eclipsed with the alkynyl (vs R) substituent accounts for the preferred formation of the major A-sulfinyl diastereomer (equation 41). 

This chapter focuses the attention on the reactions of nonstabilized carbanionic compounds such as alkyl, vinyl, aryl, alkynyl metals, etc., and the chemistry of the stabilized system, i.e. allylic, propargylic or oxaallylic carbanions is presented in Volume 2 of this series. Electrophiles with C=X bonite which are discussed include aldehydes, ketones, epoxides, aziridines, acetals, orthoesters and imines, all of which turn into highly reactive electrophiles in the presence of Lewis acids. 

Miscellaneous reactions which involve the cyclization of one component to an aziridine by a polar reaction include the electrochemical oxidative cyclization of / -(p-toluenesulfonyl) aminomalonates to 2,2-bis(carbomethoxy)-JV-(p-toluenesulfonyl)aziridines <88CL1065> and the bromonium ion-mediated cyclization of JV-propargyl acetamides to 2-(2-bromoalkylidene)aziridines... 

M. Yoshida, M. Al-Amin, K. Shishido, Synthesis of substituted furans and pyrroles by platinum-catalyzed cyclizations of propargylic oxi-ranes and aziridines in aqueous media. Synthesis (2009) 2454r-2466. 

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