Synthesis of cis-hydrindan-2,4-diones bearing an all-carbon quaternary center by a Danheiser annulation

• Gisela V. Saborit,
• Carlos Cativiela,
• Ana I. Jiménez,
• Josep Bonjoch and
• Ben Bradshaw

Beilstein J. Org. Chem. 2018, 14, 2597–2601, doi:10.3762/bjoc.14.237

• and six-membered carbocyclic ring system can be achieved in only four steps from a simple acyclic β-keto ester. Keywords: alkaloid; Danheiser annulation; decahydroquinoline; Introduction cis-Fused hydrindanes (bicyclo[4.3.0]nonanes) [1][2], scaffolds of numerous natural products, are amenable to

• have been used to build the hydrindane bicyclic system, but incorporating a different functionalization pattern in the cyclic compounds. Proposed here is a new methodological approach to functionalized 3a-substituted hydrindane synthesis based on a Danheiser annulation involving a [3 + 2] cycloaddition

• would be assembled by the simultaneous formation of two C–C bonds. This strategy is based on the disconnection across the C1–C7a and C3–C3a bonds, which according to the Danheiser annulation logic would reveal the cyclohexenone intermediate I and a silylallene such as II. The former, in turn, would