Wittig reaction aziridine synthesis

Reviews have featured epoxidation, cyclopropanation, aziridination, olefination, and rearrangement reactions of asymmetric ylides 66 non-phosphorus stabilized carbanions in alkene synthesis 67 phosphorus ylides and related compounds 68 the Wittig reaction 69,70 and [2,3]-Wittig rearrangement of a-phosphonylated sulfonium and ammonium ylides.71 Reactions of carbanions with electrophilic reagents, including alkylation and Wittig-Homer olefination reactions, have been discussed with reference to Hammett per correlations.72... 

Synthesis from erythrose An efficient approach for the synthesis of (-l-)-trihy-droxyheliotridane (180) via a chiral erythrose derivative has been reported (Scheme 16). Wittig reaction of 2,3-(9-isopropylidene-L-erythrose (172) with Ph3P=CHCH=CHC02Et produced a 1 5 mixture of the ( , )-173 and (Z,A)-174 isomeric dienes, respectively. The diene 173 could be quantitatively obtained by isomerization of 174 with E. The diene 174 was converted to the azide 177, which upon boiling in benzene gave the vinyl aziridine 176. Pyrolysis of 176 furnished the pyrrolizidine 178. On the other hand, the diene 173 was... 

In a shorter synthesis of dihydrexidine [9], synthetic intermediate 51 was obtained via an FC reaction of a chiral aziridine intermediate 60 (Scheme 2.8). Styrene 58 was prepared from a Wittig reaction of aldehyde 57 as a mixture of diastereomers ( 7Z=78 22) and treated with PhINNs in the presence of the BOX ligand 59 and Cu(OTf)2. It was found that Cu(OTf)., was a dual catalyst for the enantioselective aziridination and FC reaction. The E/Z mixture of styrenes 58 provided exclusively tran5-2-amino-l-phenyltetralin 51 in 87% ee, which could be increased up to 99% after crystallization. The c/s-cyclized product was not detected. 

The aza-[2,3] Wittig rearrangement of aziridines is an excellent method for the synthesis of substituted piperidines. The analogous reaction of an epoxide has recently been examined <06TL7281>. Reaction of divinyl epoxide 48 with /-butyl diazo acetate provides the ylide intermediate 49, which then undergoes the [2,3] Wittig rearrangement to 50, Several catalysts were examined as catalysts for the formation of 49. It is noteworthy that the copper catalyst performed much better than the more widely used rhodium catalysts. 

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