Gold‐Catalyzed Intramolecular [3+2] Cycloadditions of 1‐Aryl‐1‐allene‐6‐enes

Abstract

Treatment of 1-aryl-1-allen-6-enes with [PPh(3)AuCl]/AgSbF(6) (5 mol %) in CH(2)Cl(2) at 25 degrees C led to intramolecular [3+2] cycloadditions, giving cis-fused dihydrobenzo[a]fluorene products efficiently and selectively. The reactions proceeded with initial formation of trans/cis mixtures of 2-alkyl-1-isopropyl-2-phenyl-1,2-dihydronaphthalene cations B, which were convertible into the desired cis-fused cycloadducts through the combined action of a gold catalyst and a Brønsted acid. Theoretic calculation supports the participation of the trans-B cation as reaction intermediate. Although HOTf showed similar activity towards several 1-aryl-1-allen-6-enes, it lacks generality for this cycloaddition reaction.

Access to Polycyclic Derivatives by Triflate‐Catalyzed Intramolecular Hydroarylation

“…Intramolecular catalytic reactions [11] have been achieved with Rh I complexes, [12] In-(OTf) 3 (OTf = triflate), [13] InBr 3 , [14] BiCl 3 , [15] RuCl 3 /AgOTf [16] or performed with catalytic systems such as [PPh 3 AuCl]/AgSbF 6 [17] or AuCl 3 /AgOTf; [18] these reactions essentially involve the aryl coupling with terminal double bonds. Very few references deal with the intramolecular hydroarylation of internal alkenes (with AlCl 3 or TfOH).…”

Allenes in Catalytic Asymmetric Synthesis and Natural Product Syntheses

“…Liu and co-workers reported the goldcatalyzed intramolecular annulation of 1-aryl-1-allen-6-enes 181 in CH 2 Cl 2 , which selectively yields cis-fused [4.3.0]carbocycles 182 via the intermediacy of 183 (Scheme 51). [140] GagnØ and co-workers reported the [{(R)-3,5-xylyl-binap}(AuCl) 2 ]-catalyzed enantioselective cyclization of eneallenes with moderate enantioselectivity. [141] A cyclization/ alkoxylation catalyzed by a chiral gold(I)-phosphine complex was used in the formal synthesis of (À)-isocynometrine by…”

Recent advances in the gold-catalyzed additions to C–C multiple bonds

“…Intramolecular [M + N]-type cycloaddition reactions are powerful tools for accessing complex molecular frameworks [ 98 ]. Several gold-catalyzed [3 + 2] [ 99 ], [4 + 2] [ 100 – 105 ], and [4 + 3] [ 106 – 108 ] cycloaddition reactions have been developed in last 3 years. Treatment of 1-aryl-1-allen-6-enes 220 with [PPh 3 AuCl]/AgSbF 6 (5 mol %) in CH 2 Cl 2 at 25 °C led to intramolecular [3 + 2] cycloadditions to afford cis -fused dihydrobenzo[ a ]fluorenes 221 efficiently and selectively [ 99 ].…”

“…Several gold-catalyzed [3 + 2] [ 99 ], [4 + 2] [ 100 – 105 ], and [4 + 3] [ 106 – 108 ] cycloaddition reactions have been developed in last 3 years. Treatment of 1-aryl-1-allen-6-enes 220 with [PPh 3 AuCl]/AgSbF 6 (5 mol %) in CH 2 Cl 2 at 25 °C led to intramolecular [3 + 2] cycloadditions to afford cis -fused dihydrobenzo[ a ]fluorenes 221 efficiently and selectively [ 99 ]. As pointed out by the researchers, the reactions proceeded with the initial formation of trans / cis mixtures of 2-alkyl-1-isopropyl-2-phenyl-1,2-dihydronaphthalene cations, which were converted into the desired cis- fused cycloadducts through the combined action of a gold catalyst and a Brønsted acid.…”