Regio‐ and Stereoselective Synthesis of Rotationally Hindered C₁₂‐Naphthylated Tribenzo[a,c,j]xanthenes through Catalytic Tricyclization of Yne‐Allenones

Abstract

A Lewis acid‐catalyzed tricyclization of yne‐allenones with 1‐alkynylnaphthalen‐2‐ols has been developed, and used to produce a wide range of rotationally hindered tribenzo[a,c,j]xanthenes with generally good yields and stereoselectivity. This process involves a complex [2+2] cycloaddition relay and [4+2] cyclization cascade, enabling scission/recombination of C−C triple bonds to access unprecedented hexaheterocyclic architectures. The reaction also features good compatibility with different types of substituents, triple annulation cascade and the efficient control of regio‐ and stereochemistry.

Highlighting the Rich Chemistry of the Allenone Moiety

“…[200] Chromene structures have also been synthesized from the reaction of benzene-tethered alkynyl allenones 93 and alkynols 410 (Scheme 75). [201] Lewis acid-catalyzed intramolecular [2 + 2] cycloaddition of allenones 93 generates the corresponding fused cyclobutene intermediates 96, which undergo a consecutive intermolecular [2 + 2] cycloaddition with one unit of alkynol 410 to build intermediate bicyclo[2.2.0]hex-2enes 430. Ring opening reaction of the highly strained fused cyclobutane scaffold and addition of another molecule of alkynol 410 explains the formation of the observed polycyclic pyran structures 429 (Scheme 75).…”

“…Ring opening reaction of the highly strained fused cyclobutane scaffold and addition of another molecule of alkynol 410 explains the formation of the observed polycyclic pyran structures 429 (Scheme 75). [201] The addition of nucleophiles bearing carbonyl groups, such as activated acetates to α-allenones has been devised as an efficient tool to afford α-pyrone structures. Two main strategies have been reported depending on the nature of the α-allenone skeleton.…”

“…Ring opening reaction of the highly strained fused cyclobutane scaffold and addition of another molecule of alkynol 410 explains the formation of the observed polycyclic pyran structures 429 (Scheme 75). [201] …”

Engaging Yne‐Allenes in Cycloaddition Reactions: Recent Developments

“…By using 1‐alkynylnaphthalen‐2‐ols 107 as internal alkyne precursors, BF 3 ·Et 2 O‐catalyzed reaction proceeded along a convergent tricyclization direction to access rotationally hindered C 12 ‐naphthylated tribenzo[ a,c,j ]xanthenes 108 with high regioselectivity (Scheme 35a). [ 116 ] Curiously, two molecules of 107 were introduced into the final hexacyclic scaffold, enabling the C—C triple bond cleavage and recombination of yne‐allenones. This three‐ component reaction possesses good compatibility with different types of substituents and high atom utilization.…”