An expeditious route to trans fused 5–7–6 and 6–7–6 carbocycles through photoisomerisation-cycloaddition of benzocycloheptenone

Ghosh, Subrata; Roy, Supti Saha; Saha, G.

doi:10.1016/s0040-4020(01)89814-8

Cited by 9 publications

(1 citation statement)

References 41 publications

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“…Based on literature procedures . LiBr (2.5 equiv) and Li 2 CO 3 (2.5 equiv) were added to a solution of a 2-bromocycloalkanone (1.0 equiv) in dry DMF (500 mM).…”

Section: Experimental Sectionmentioning

confidence: 99%

Diels–Alder Reaction of Photochemically Generated (E)-Cyclohept-2-enones: Diene Scope, Reaction Pathway, and Synthetic Application

et al. 2022

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Upon irradiation at λ = 350 nm, cyclohept-2-enone undergoes an isomerization to the strained (E)-isomer. The process was studied by XMS-CASPT2 calculations and found to proceed by two competitive reaction channels on either the singlet or the triplet hypersurface. (E)-Cyclohept-2-enone is a reactive dienophile in thermal [4 + 2] cycloaddition reactions with various dienes. Ten different dienes were probed, most of whichexcept for 1,3-cyclohexadieneunderwent a clean Diels−Alder reaction and gave the respective trans-fused six-membered rings in good yields (68− 98%). The reactions with furan were studied in detail, both experimentally and by DLPNO−CCSD(T) calculations. Two diastereoisomers were formed in a ratio of 63/35 with the exoproduct prevailing, and the configuration of both diastereoisomers was corroborated by single crystal X-ray crystallography. The outcome of the photoinduced Diels−Alder reaction matched both qualitatively and quantitatively the calculated reaction pathway. Apart from cyclohept-2-enone, five additional cyclic hept-2-enones and cyclooct-2-enone were employed in their (E)-form as dienophiles in the Diels−Alder reaction with 1,3-cyclopentadiene (80−98% yield). The method was eventually applied to a concise total synthesis of racemic trans-α-himachalene (four steps, 14% overall yield).

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“…Based on literature procedures . LiBr (2.5 equiv) and Li 2 CO 3 (2.5 equiv) were added to a solution of a 2-bromocycloalkanone (1.0 equiv) in dry DMF (500 mM).…”

Section: Experimental Sectionmentioning

confidence: 99%