Effective Uses of Dirhodium(II) Tetrakis[methyl 2-oxopyrrolidine-5(R or S)-carboxylate] for Highly Enantioselective Intermolecular Cyclopropenation Reactions

Macrocyclic Cyclopropenes by Highly Enantioselective Intramolecular Addition of Metal Carbenes to Alkynes

“…In contrast to prior results from intermolecular cyclopropenation, [12] the CuPF 6 /1 combination is an effective catalyst, [13] although not sufficiently selective to be of synthetic value. With product yields averaging 80 % for the formation of 10-membered ring-fused cyclopropenes, without the need for high-dilution techniques, this methodology is one of the most effective for the enantioselective synthesis of large ring compounds.…”

“…Cyclopropene 13 was relatively unstable and, therefore, was treated with 1,3-diphenylisobenzofuran to form its stable exo-Diels ± Alder adduct; [11] the % ee of 13 was obtained following selective hydrogenation of the cyclopropene with diimide. [12] The ylide derived product 15 that was a major outcome of the CuPF 6 /1 catalyzed reaction was formed in only 18 % ee.…”

Rhodium(II)‐Catalyzed CH Insertions with {[(4‐Nitrophenyl)sulfonyl]imino}phenyl‐λ3‐iodane

“…-The transition-metal-catalyzed transfer of carbenes to organic compounds is a well-established synthetic method, and several systems for enantioselective cyclopropanation [I], cyclopropenation [2], and CH insertion [3] have been developed. The corresponding reactions of carbene analogs are, however, much less known.…”

Diastereoselective addition of heteroatom nucleophiles to ethyl 2-(diethoxymethyl)-cycloprop-2-ene-1-carboxylate

“…The enantioselective cyclopropenation of propionaldehyde diethyl acetal (2) with methyl diazoacetate, using Rh 2 (5S-MEPY) 4 as chiral catalyst, has been described previously, in 42% yield. 11 In a more recent paper, this reaction has been optimized by increasing the addition time and the reagent ratio. With the cyclopropene 1 in hand we have examined the addition of heteroatom nucleophiles (Table 1).…”