Efficient Silver‐Catalyzed Regio‐ and Stereospecific Aziridination of Dienes

Abstract

The synthesis of aziridine derivatives through metal-mediated nitrene addition reactions to olefins [Eq. (1)] has been extensively developed in the last decades; quantitative conversions as well as complete enantioselection have been already described. [1,2] However, in spite of the large number of reports related to the alkene aziridination reaction by this method and the synthetic interest of vinylaziridines, [3] only few have dealt with conjugated dienes as the substrate. Copper-, [4] manganese-, and ruthenium-based [5] catalysts have provided good yields of vinylaziridines formed by the exclusive aziridination of one C = C bond of the diene, although with the following limitations: 1) only symmetric dienes were employed and 2) selectivity, intended as cis/trans (or trans/cis) ratio, was low. These two drawbacks strongly prevent the synthetic application of this method.In fact, vinylaziridines are commonly synthesized by stoichiometric procedures based on nucleophilic intramolecular substitution. Thus, the Darzens-type reaction (Scheme 1, path a) is one of the oldest and most flexible methods for preparation of functional aziridine derivatives including vinylaziridines.

Tunable, Chemoselective Amination via Silver Catalysis

“…6,7a–f However, a tridentate ligand reversed this selectivity (entries 8 and 16). This result stimulated our curiosity, and a further perusal of the literature showed that Ag has the unique ability to change coordination geometry in response to changes in the Ag counteranion, the ligand identity, or the metal/ligand ratio.…”

Diastereoselective addition of alkenylchromium(III) reagents to Garner’s aldehyde: Nozaki-Hiyama-Kishi coupling approach to sphingosines and ceramides

“…Next, attention was turned toward the most abundant sphingosine 2 in nature, which could be obtained through the addition of (E)-1-iodo-1-pentadecene (8) 21 to Garner's aldehyde (1, Scheme 2). With the previously optimized chromium(II) loading, N,O-protected sphingosines 9a and 9b were obtained with an even higher diastereoselectivity (anti:syn = 7:1).…”

Chemoselective silver-catalyzed nitrene insertion reactions

“…The Perez group further demonstrated the synthetic utility of silver(I) catalysis in the chemoselective aziridination of conjugated dienes bearing a terminal alcohol group [12]. Silver(I) complexes supported by trispyrazolylborate scorpionate ligands (Tp x ; Fig.…”

“…Reactions were run at temperatures ranging from 0 °C to room temperature. Table 2 Aziridination of conjugated dienes with a high preference for aziridination proximal to the hydroxyl group [12].…”

“…Diene % conversion Ratio of 2:3 trans:cis 3 Synthesis of ( ± )-sphingosine using Ag(I)-catalyzed aziridination [12].…”