Activated vinylaziridines (N-benzoyl, N-p-toluenesulfonyl, N-t-butoxycarbonyl and N-benzyloxycarbonyl) have been prepared from N-substituted 1,4-aminoalcohols using Mitsunobu conditions. Activated vinylaziridines containing an electron withdrawing group are versatile synthetic building blocks, because the N-substituent facilitates regiospecific aziridine opening by a nucleophile. 1,2 2-Vinylaziridines are particularly useful intermediates for organic synthesis and thus have been used in the synthesis of various natural products. 3 Hudlicky has reviewed the chemistry of vinyl aziridines, 4 and used a vinyl N-ptoluenesulfonyl (Ts) aziridine in the first asymmetric synthesis of the antitumor alkaloid pancratistatin. 5 Unfortunately, the lowest yielding step in the synthesis was the aziridination of enantiomerically pure 3-bromo-1,2-isopropylidenedioxycyclohexa-3,5-diene. 2 A widely employed activating group is the p-toluenesulfonyl group because of the accessible methods for the preparation of N-Ts aziridines. 6 However, removal of this protecting group frequently requires harsh conditions. 7 Synthetic efforts have been directed toward the development of direct methods of preparing aziridines containing other activating groups. 8There is a plethora of methods for the preparation of aziridines, and they have been recently reviewed by Sweeney 9a and Tanner. 9b An obvious method utilizes 1,2-aminoalcohols as precursors. 10 The reaction is readily achieved when the alcohol is converted to a nucleofuge. However, this method is limited to N-phosphonylated 11 and N-Ts aziridines; 6 when applied to the synthesis of N-acyl or N-carbamoyl aziridines, the nucleophilic attack by the carbonyl oxygen leads to the formation of oxazolines. 12 Conceptually, vinylaziridines should also be easily accessed from 1,4-aminoalcohols as shown in Scheme 1. Scheme 1We present in this communication a new method for the preparation of 2-vinylaziridines from 1,4-aminoalcohols. This method allows the preparation of functionalized aziridines while avoiding protectiondeprotection steps and permits the direct preparation of aziridines containing N-Ts, N-acyl and N-carbamoyl activating groups. Enantiomerically pure aziridines are prepared by enantiospecific synthesis from enantiomerically pure dienes.1,4-Aminoalcohols are prepared easily in a high yielding two-step sequence starting from a conjugated diene. Nitroso dienophiles are then generated in situ as transient intermediates by oxidation of the corresponding hydroxamic acid with periodate (NaIO 4 , MeOH-H 2 O). 13 Nitroso dienophiles generated in the presence of a conjugated double bond furnish 3,6-dihydro-1,2-oxazines. 14 This hetero Diels-Alder cycloaddition reaction occurs regio-and stereospecifically with chiral dienes. 15 The cis-1,4-aminoalcohols are obtained by reductive cleavage of the nitrogen-oxygen bond of the corresponding 1,2-oxazines using either Keck's aluminium amalgam procedure 16 or refluxing the oxazine in acetonitrile in the presence of molybdenum hexacarbonyl. 17 Cycli...

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.