Highly stereoselective synthesis of optically active oxazolinyl oxiranes from azaenolates of a chiral 2-chloromethyloxazoline Saverio Florio,* Vito Capriati and Renzo Luisi CNR, Centro di Studio sulle Metodologie Innovative di Sintesi Organiche, Dipartimento Farmaco-Chimico, Universita Á di Bari, Via E. Orabona 4, I-70125 Bari, Italy Received 19 April 2000; accepted 16 May 2000 Abstract Boron and titanium azaenolates 2 and 4, generated at 0  C and ^100  C, respectively, from the optically active chloromethyloxazoline 1, have been found to couple with aliphatic ketones in a highly diastereo- selective fashion ending up with the formation of optically active oxazolinyl oxiranes 3. Less stereoselective was the reaction with aromatic ketones. # 2000 Elsevier Science Ltd. All rights reserved. Keywords: boron azaenolate; titanium azaenolate; chiral oxazolines; chiral oxiranyl oxazolines. The chemistry of azaenolates of 2-alkyloxazolines, which are extremely useful intermediates in synthetic organic chemistry, has been rather exhaustively investigated with pivotal and fundamental achievements from Meyers' research group. 1 In comparison, azaenolates of heterosubstituted 2-alkyloxazolines have been studied much less. 2 Recent results from our laboratory had proved that azaenolates of chloroalkyloxazolines couple eciently with carbonyl compounds 3 and imines 4 to produce oxazolinyl oxiranes, and then formyl oxiranes by elaboration of the oxazolinyl ring, and aziridines, respectively. In particular, we had found that lithium azaenolates couple with carbonyl compounds with poor diastereoselection, 5 whereas boron azaenolates react with very high and opposite diastereoselection depending upon the ligands on the boron atom. 6 However, we disappointingly found that boron azaenolates of 1, generated at ^78  C, do not couple with aliphatic enolizable ketones probably due to the competing ketone enolization which interferes with the enolization of the chloromethyloxazoline in the generation step of the boron azaenolate. In the present paper we wish to report that under proper experimental conditions boron aza- enolates of the chiral, non-racemic, chloromethyloxazoline 1 also couple eciently and highly diastereoselectively with enolizable ketones. We also report on the coupling of titanium azaenolates. 0040-4039/00/$ - see front matter # 2000 Elsevier Science Ltd. All rights reserved. PII: S0040-4039(00)00809-1 Tetrahedron Letters 41 (2000) 5295±5298 * Corresponding author.