Cationic Rhodium(I)/H₈‐binap Complex Catalyzed [2+2+2] Cycloadditions of 1,6‐ and 1,7‐Diynes with Carbonyl Compounds

Abstract

We have established that a cationic rhodium(I)/H 8 -binap complex catalyzes [2+2+2] cycloadditions of a variety of 1,6-and 1,7-diynes with both electron-deficient and electron-rich carbonyl compounds, leading to dienones in high yield under mild reaction conditions. In the reactions with acyl phosphonates, the reactivity of 1,6-and 1,7-diynes was highly dependent on their own structures. The addition of chelating diethyl oxalate effectively promoted the [2+2+2] cycloadditions involving acyl phosphonates, presumably due to the

Rhodium‐Catalyzed Asymmetric Formal Olefination or Cycloaddition: 1,3‐Dicarbonyl Compounds Reacting with 1,6‐Diynes or 1,6‐Enynes

“…The use of excess 2 a (2.0 equiv) in the reaction using (R)-segphos increased the product yield along with slight improvement of the product ee value (entry 4). Significant improvement of both the product yield and ee value using excess 2 a was observed in the reaction using (R)-H 8 -binap, which furnished 3 aa with the highest yield and ee value (entry 5). The absolute configuration of the major Scheme 1.…”

“…In 2007 our research group reported that a cationic rhodium(I)/H 8 -binap complex [5,6] is a highly active and versatile catalyst for the [2+2+2] cycloaddition [7] of 1,2-dicarbonyl compounds with 1,6-diynes. [8][9][10][11][12] After this report, we succeeded using the cationic rhodium(I)/H 8 -binap complex as a catalyst in the asymmetric [2+2+2] cycloaddition of 1,2-dicarbonyl compounds with 1,6-enynes, thereby constructing two stereocenters with high enantio-and diastereoselectivity. [13,14] We report herein the cationic rhodium(I)/H 8 -binap or segphos complex as a catalyst for the asymmetric formal olefination and cycloaddition of 1,3dicarbonyl compounds with 1,6-diynes and 1,6-enynes, respectively, which construct one or three stereocenters with high diastereo-and enantioselectivity.…”

A Single Step Approach to Piperidines via Ni-Catalyzed β-Carbon Elimination

“…5a,5b,6 This is in contrast to other reports where use of activated ketones was critical for the success of the reaction. 7 Murakami and co-workers discovered that transition metal catalysts can be utilized to exploit the ketone moiety of cyclobutanone that can render β -carbon elimination in reactive intermediates. 8 Recently, Murakami reported that cyclobutanone can be very elegantly coupled with alkynes to afford highly substituted cyclohexenones.…”

Rhodium‐Catalyzed Asymmetric Formal Olefination or Cycloaddition: 1,3‐Dicarbonyl Compounds Reacting with 1,6‐Diynes or 1,6‐Enynes

“…In contrast, asymmetric olefination or cycloaddition of the ketone carbonyl group of b-ketoesters through C=C or CÀC/CÀO bond formation would furnish chiral b,g-unsaturated esters or balkoxyesters in a single step (Scheme 1). [8][9][10][11][12] After this report, we succeeded using the cationic rhodium(I)/H 8 -binap complex as a catalyst in the asymmetric [2+2+2] cycloaddition of 1,2-dicarbonyl compounds with 1,6-enynes, thereby constructing two stereocenters with high enantio-and diastereoselectivity. In 2007 our research group reported that a cationic rhodium(I)/H 8 -binap complex [5,6] is a highly active and versatile catalyst for the [2+2+2] cycloaddition [7] of 1,2-dicarbonyl compounds with 1,6-diynes.…”

“…This observation is in sharp contrast to the reactions of entries 1 and 8 in Table 2 that exhibited significantly different reactivity. Possible mechanisms for the selective formation of (S)-3 aa and (3aR,5aR,6R)-7 b using (R)-H 8 [c] The relative and absolute configuration of (À)-7 b was determined to be 3aR,5aR,6R by the X-ray crystallographic analysis of the corresponding 4-bromobenzoyl ester (À)-8. With respect to the 1,6-enyne moieties, not only sulfonamidelinked 1,6-enynes but also malonate-linked 1,6-enynes 6 c and 6 d could be employed (entries 3 and 4).…”