Enantioselective Synthesis of Planar-Chiral Metacyclophanes through Rhodium-Catalyzed Alkyne Cyclotrimerization

Abstract

We have achieved the first catalytic enantioselective synthesis of planar-chiral metacyclophanes by means of cationic rhodium(I)/(R)-H8-BINAP complex-catalyzed alkyne cyclotrimerization. This reaction represents a versatile new method for the preparation of planar-chiral [7]−[10]metacyclophanes.

Recent development for enantioselective synthesis of aromatic compounds from alkynes via metallacyclopentadienes

“…Tanaka et al designed an intramolecular [2 + 2 + 2] cycloaddition of triynes 87 , bearing substituents at two alkyne termini, which could form the corresponding ortho ‐ or meta‐ cyclophanes 89 and 90 . Meta ‐cyclophane 90 would possess stable planar chirality because of no ring flip occurring (Scheme ) [19].…”

“…The reaction of substituted triyne 91 in the presence of 5 mol % [Rh(cod) 2 ]BF 4 /( R )‐H 8 ‐BINAP complex gave the desired [7–10] metacyclophanes 92 with high enantioselectivity (Scheme ) [19a].…”

“…The intermolecular variant of this reaction was also investigated. The reaction of bis(methoxymethyl)‐substituted diyne 93 with di‐ tert ‐butyl acetylenedicarboxylates in the presence of 10 mol % [Rh(cod) 2 ]BF 4 /( S )‐xyl‐H 8 ‐BINAP at room temperature gave the desired [9]‐metacyclophane 94 in 15% yield and 92% ee , along with [9]‐paracyclophane 95 in 5% yield (Scheme ) [19a].…”

[2+2+2] Cycloaddition Reactions of Macrocyclic Systems Catalyzed by Transition Metals. A Review

“…A highly reliable and atom-economical method for the synthesis of polysubstituted benzene derivatives is the transition-metal-catalyzed [2+2+2] cycloaddition of three alkynes [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 ]. Completely intramolecular reactions are particularly interesting as they provide complex polycyclic systems in a single synthetic operation (Equation 1, Scheme 1 ) [ 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 ]. Furthermore, if the three alkynes form part of a closed system, i.e.…”

Asymmetric synthesis of planar-chiral paracyclophanes by double C–S bond formation: comparison of catalytic activity and enantioselectivity of Pd and Rh catalysts

“…5,6 In 2007 we successfully applied this methodology to the first enantioselective synthesis of planar-chiral metacyclophanes (Scheme 2). 7,8 Recently, Shibata et al applied the rhodium-catalyzed [2+2+2] cycloaddition to the enantioselective synthesis of chiral cage compounds possessing planar-chirality. 9 However, application to the enantioselective synthesis of planar-chiral paracyclophanes has not been reported.…”