Epoxides Blum aziridine synthesis

Somfai and Ahman have applied the Blum aziridine synthesis to the total synthesis of indolizidine 209D (20). ° Epoxide 18 was opened with sodium azide and the primary alcohol protected as the silyl ether. The azide was then treated with triphenylphosphine and heat, resulting in concomitant reduction and cyclization to give intermediate 19. Aziridine 19 was eventually processed to indolizidine 209D (20). 

Finally, Tanner and Somfai completed a formal total synthesis of thienamycin (26) using the Blum aziridine synthesis as a key step. As in the previous examples, epoxide 24 was converted to aziridine 25 in good yield using a Blum aziridine synthesis. Intermediate 25 was eventually processed to thienamycin (26). 

Researchers at Lexicon Pharmaceuticals found that limonene aziridines could be efficiently prepared from the corresponding limonene oxides using the Blum aziridine synthesis. Epoxide 32 was opened with sodium azide to produce the regioisomeric azido-alcohols 33 and 34 in an approximate 1 1 ratio. The secondary azide was reductively cyclized with triphenylphosphine at ambient temperature, whereas the tertiary azide required heating to effect the same transformation. In this way, the desired aziridines 35 and 36 were prepared in good yield on multigram scale. 

Backvall and co-workers used the Blum reaction in the total synthesis of ferruginine (23)." Epoxide 21 was opened with sodium azide and the resultant azido-alcohol was reduced and cyclized with triphenylphosphine in good yield to give aziridine 22. Intermediate 22 was eventually processed to ferruginine (23). 

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