Chloroallenylzinc reagents

Additions of the foregoing chloroallenylzinc reagent to aldehydes, and M-TMS and N-benzylimines allowed access to alkynyloxiranes and aziridines34. The former result from a two-step process in which the initial anti adducts are converted to trans alkynyloxiranes upon treatment with DBU or KF (Table 22). The latter conditions effect desilylation as well as cyclization. Interestingly, when the addition to isobutyraldehyde is conducted with... 

TABLE 21. Addition of chloroallenylzinc bromide reagents to sulfoximines... 

Addition of the chloroallenylzinc chloride reagent to /V-benzylirnincs afforded the fraws-aziridinc products directly (Table 23). Evidently the higher nucleophihcity of the /V-benzyl substituent promotes in situ displacement of the vicinal chloride of the major anti adduct. The /V-bcnzyl substituent was assumed to adopt an orientation trans to the R group of the aziridine. 

Lithiation and Li-Zn exchange make 3-chloroallenylzinc bromides available from propargyl chlorides. These reagents react with aldimines to form 2-alkynylaziridines. Al-lenylzinc reagents prepared from chiral propargylic mesylates have been used to synthesize anti-homopropargylic alcohols. ... 

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