It has been established that a cationic rhodium(I)/H8 -binap complex catalyzes the [3+2+2] cycloaddition of 1,6-diynes with cyclopropylideneacetamides to produce cycloheptadiene derivatives through cleavage of cyclopropane rings. In contrast, a cationic rhodium(I)/(S)-binap complex catalyzes the enantioselective [2+2+2] cycloaddition of terminal alkynes, acetylenedicarboxylates, and cyclopropylideneacetamides to produce spiro-cyclohexadiene derivatives which retain the cyclopropane rings.

It has been established that a cationic rhodium(I)/H8-BINAP complex catalyzes the asymmetric [2 + 2 + 2] cycloaddition of 1,6-enynes with cyclopropylideneacetamides to produce spirocyclohexenes in excellent enantioselectivity with retaining cyclopropane rings.

It has been established that ac ationic rhodium(I)/ H 8 -binap complex catalyzesthe [3+ +2+ +2] cycloaddition of 1,6-diynes with cyclopropylideneacetamides to produce cycloheptadiene derivatives through cleavage of cyclopropane rings. In contrast, acationic rhodium(I)/(S)-binap complex catalyzes the enantioselective [2+ +2+ +2] cycloaddition of terminal alkynes,a cetylenedicarboxylates,a nd cyclopropylideneacetamides to produce spiro-cyclohexadiene derivatives which retain the cyclopropane rings.Transition-metal-catalyzed [3+ +2+ +2] cycloaddition reactions involving cyclopropylidene compounds are valuable methods for the construction of seven-membered rings.[1] Previously, ac yclopropylideneacetate as ac ycloaddition partner and anickel(0)/phosphine complex as acatalyst were used. [2,3] For example,S aito and co-workers reported the nickel(0)/phosphine-complex-catalyzed intermolecular [3+ +2+ +2] cycloaddition of two identical alkynes with the cyclopropylideneacetate.[2h] Subsequently,they developed the cycloaddition of two different alkynes with the cyclopropylideneacetate,a lthough the slow addition of substrates and the large excess of one alkyne component were required.[2g] They also developed the partial intramolecular [3+ +2+ +2] cycloaddition of a1 ,6-diyne with cyclopropylideneacetate.[2e] Ap roposed mechanism of the nickel(0)-catalyzed [3+ +2+ +2] cycloaddition reactions is shown in Scheme 1. [2a,c-h, 4] Tw oalkynes and cyclopropylideneacetate react with the nickel(0) complex to generate the nickelacycloheptadiene intermediate A.Ab-carbon atom elimination affords the nickelacyclooctadiene intermediate B and subsequent reductive elimination furnishes the cycloheptadiene derivative C.A lthough direct reductive elimination from A would furnish the spiro-cyclohexadiene derivative D,s uch reactions are limited to the case using sterically demanding phosphine ligands and proceeded in low yields. [2f, 5] Importantly,both cycloheptane [6] and spiro-cyclohexane [7] skeletons are frequently found in biologically active natural products.T herefore,t heir selective syntheses are important targets for organic synthesis.H erein, we have applied ac ationic rhodium(I)/biaryl bis(phosphine) catalyst, which is known to be ah ighly active catalyst for the [2+ +2+ +2] cycloaddition, [8,9] to the cycloaddition reactions involving cyclopropylidene compounds. [10] Our research group reported that acrylamide derivatives are highly reactive substrates in cationic rhodium(I)-complexcatalyzed [2+ +2+ +2] cycloaddition reactions.[11] Therefore,w e first examined the reaction of the 1,6-diyne 1a and N-methyl-N-phenylcyclopropylidene-acetamide (2a)inthe presence of cationic rhodium(I)/bisphosphine complexes,a ss hown in Table 1. We were pleased to find that the [3+ +2+ +2] cycloaddition of 1awith 2aproceeded using acationic rhodium(I)/ segphos catalyst (20 mol %) to give the [3+ +2+ +2] cycloaddition product 3aa in moderate yield along with the [2+ +2+ +2] cycloaddition product 4aa (entry 1). Screening of bis(phosphine...

furnishing spirocyclohexenes in excellent enantioselectivities with retaining cyclopropane rings

Rhodium-Catalyzed [3 + 2 + 2] and [2 + 2 + 2] Cycloadditions of TwoAlkynes with Cyclopropylideneacetamides. -A cationic Rh(I)/(S)-BINAP complex catalyzes the enantioselective [2+2+2]-cycloaddition of terminal alkynes, acetylenedicarboxylates and cyclopropylideneacetamides to furnish spiro-cyclohexadiene derivatives without cleavage of the cyclopropane ring. Contrary, Rh(I)/H 8-BINAP catalyzed reaction of cyclopropylideneacetamides with 1,6-diynes affords cycloheptadiene derivatives via a [3+2+2]-cycloaddition pathway involving cleavage of the cyclopropane ring. -(YOSHIDA, T.; TAJIMA, Y.; KOBAYASHI, M.; MASUTOMI, K.; NOGUCHI, K.; TANAKA*, K.; Angew. Chem., Int. Ed. 54 (2015) 28, 8241-8244, http://dx.doi.org/10.1002/anie.201502505 ; Dep. Appl. Chem., Grad. Sch. Eng., Tokyo Univ. Agric. Technol., Koganei, Tokyo 184, Japan; Eng.) -Toeppel 45-028