Enantioselectivity and cis/trans‐Selectivity in Dirhodium(II)‐Catalyzed addition of diazoacetates to olefins

Abstract

The Rh11‐catalyzed carbenoid addition of diazoacetates to olefins was investigated with [Rh2{(4S)‐phox}4] (1;phox = tetrakis[(4S)‐tetrahydro‐4‐phenyloxazol‐2‐one]), [Rh2{(2S)‐mepy}4] (2; mepy = tetrakis[methyl (2S)‐tetrahydro‐5‐oxopyrrole‐2‐carboxylate]), and [Rh2(OAc)4] (3). While catalysis with 2 and 3 afford preferentially trans‐cyclopropanecarboxylates, the cis‐isomers are the major products with 1. In general, the enantioselectivities achieved with 1 and 2 are comparable. Additions catalyzed by 1 are strongly sensitive to steric effects. Highly substituted olefins afford cyclopropanes in only poor yield. The preferential cis‐selectivity observed in reactions catalyzed by 1 is attributed to dominant interactions between the ligand of the catalyst and the substituents of both olefin and diazoacetate, which overrule the steric interactions between olefin and diazoacetate in the transition state for carbene transfer.

Supramolecular Coordination: Self-Assembly of Finite Two- and Three-Dimensional Ensembles

“…228 The enatiocontrol achieved was superior to that of known dirhodium(II) catalysts with chiral carboxamide ligands. 321 …”

Catalytic Conversion of Furans and Pyrroles to Natural Products and Analogues Utilizing Donor‐Acceptor Substituted Cyclopropanes as Key Intermediates

“…From the early work of Wenkert and Fowler, it was already known that cyclopropanations to adducts of type 4 and 5 are highly diastereoselective, orienting the ester moiety onto the convex face of the bicycles as well. Although only few enantioselective cyclopropanations of furans with simple diazoesters had been attempted with limited success when we started our program, we were confident that these reactions could be rendered asymmetric, based on the highly efficient copper(I)‐semicorrin and ‐bis(oxazoline) catalysts pioneered independently by the groups of Pfaltz, Masamune, and Evans, which had been already proven to give excellent results for cyclopropanations of dihydrofurans and silylenolethers . Moreover, related aza(bis)oxazolines of these ligands are available that can be readily immobilized on various supports and thus pave the road for scale‐up of such cyclopropanations by facilitating the removal and recycling of the chiral catalysts…”

Asymmetric Catalysis with a Phosphoramidite Derived from (−)-(aR)- [1,1′-Binaphthalene]-8,8′-diol

“…IR (CHCl 3 ): 3683m, 3618s, 3482w, 3014s, 2400s, 1522s, 1420w, 1272w, 1207s, 1046s, 928m, 878w, 764s, 676s. 3080m, 3050m, 3015m, 2970s, 2920s, 2850s, 1680s, 1579m, 1450s, 1375m, 1320w, 1260m, 1245w, 1190w, 1180m, 1160w, 1060w, 1002w, 950w, (18) was carried out with 5% of catalyst as described previously [22] [24]. …”

“…The Cu-catalyzed cyclopropanation of styrene (18) with ethyl diazoacetate (EDA) [22] afforded 3 : 2 mixture of cis-and transcyclopropanecarboxylates 19 without asymmetric induction (Scheme 4). Cu-Catalyzed nitrene transfer [23] from TsNIPh to styrene (18), in turn, yielded the aziridine derivative 20 in high yield (96%), but with only marginal enantioselectivity (11%).…”