Science of Synthesis

Elie, M.; Renaud, J.-L.; Gaillard, S., Science of Synthesis: N-Heterocyclic Carbenes in Catalytic Organic Synthesis, (2016) 1, 254.

Recently, Michalak and co-workers reported the first diastereoselective synthesis of N-propargylic hydroxylamines ‌107‌ catalyzed by copper–NHC complexes through the addition of terminal alkynes (‌Scheme 59‌).[‌107‌] Screening of a series of complexes revealed that the well-defined CuI(SIPr) [SIPr = 1,3-bis(2,6-diisopropylphenyl)-4,5-dihydroimidazol-2-ylidene] complex is the most efficient for the totally stereoselective addition of alkynes to chiral nitrones. The formal synthesis of (−)-lengitinosine, an indolizidine alkaloid exhibiting amyloglucosidase inhibition activity, has been undertaken. The key azabicyclic intermediate is isolated in three steps in 43% overall yield with good diastereoselectivity (89:11 in the first step).

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References