Complex Carbocyclic Skeletons from Aryl Ketones through a Three‐Photon Cascade Reaction

Abstract

Starting from readily available 7‐substituted 1‐indanones, products with a tetracyclo[5.3.1.01,704,11]undec‐2‐ene skeleton were obtained upon irradiation at λ=350 nm (eight examples, 49–67 % yield). The assembly of the structurally complex carbon framework proceeds in a three‐photon process comprising an ortho photocycloaddition, a disrotatory [4π] photocyclization, and a di‐π‐methane rearrangement. The flat aromatic core of the starting material is converted into a functionalized polycyclic hydrocarbon with exit vectors in three dimensions. Ring opening reactions at the central cyclopropane ring were explored, which enable the preparation of tricyclo[5.3.1.04,11]undec‐2‐enes and of tricyclo[6.2.1.01,5]undecanes.

Photocycloadditions of benzene derivatives and their systematic application to organic synthesis

“…When similar compounds to 71 were irradiated at λ = 350 nm, a new reactivity was observed. [74] Rauscher and co-workers used this photochemical reaction cascade for the total synthesis of (+)-agarozizanol B (Scheme 18). [75] In this reaction, irradiation of substrate 73 yields product 74 after the classical sequence of ortho photocycloaddition, ring opening and photocyclisation.…”

The Awakening of a Sleeping Beauty: The ortho Photocycloaddition in the Total Synthesis of Protoilludane- and Prezizaene-Type ­Sesquiterpenes

“…With the latter in hand, the reaction cascade was performed using MeOH as the solvent at λ = 350 nm and with an irradiation time of 17 hours (Scheme 14 ). 32 While compound rac - 34a , bearing two oxygen atoms in the 4-atom linker that originally connected the arene to the alkene, was obtained with a moderate yield of 49%, replacing one of the oxygen atoms by a CH 2 group in the linker proved beneficial to the reaction yield. Indeed, compound rac - 34b was obtained with a good yield of 66%.…”

Synthesis of Boronates with a Protoilludane Skeleton

“…In the former case, product cis - 14a was isolated in 42% yield as a single diastereoisomer. In the latter case, consecutive reactions 6b 18 were notable, which we had hoped to avoid by using a long irradiation wavelength. Although the starting material of the reaction was ( E )-configured, the major diastereoisomers turned out to be cis -products, that is, the BPin substituent at C8 was located cis to the substituent at C7 (protoilludane numbering).…”