Diethylazodi carboxylate

The Mitsonubo reaction between triphenylphosphine and diethylazodi-carboxylate (49) has been shown to be a source of diaryloxy- or dialkoxy-phosphoranes (51) via (50), which contradicts a recent proposal that the key intermediate in the reaction is an 0,A-phosphorane. 

Alkylation of hydroxamic acids as a method of co-N-hydroxyamino acids (2) synthesis was introduced by Maurer and Miller 196), When N- r -butoxycarbonyl-6-hydroxynorleucine benzylhydroxamate (248) or a homologue was treated with triphenylphosphine and diethylazodi-carboxylate (DEAD) under Mitsunobu conditions 197), intramolecular alkylation took place leading to N-hydroxylactams (249) or (250) as well as lesser amounts of hydroximates Z-(251) and -(252) (Scheme 50). The products were separated and distinguished by NMR spectrometry 196,198,199). Derivatives of the seven-membered N-hydroxylactam (253) were applied for the total synthesis of mycobactin S2 (254) 199) (Scheme 51). 

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