Abstract:

Bohlmann et al. reported the oxidative spirocyclisation of 2-(ω-hydroxyalkyl)furans under Clauson-Kaas conditions to furnish 1,6-dioxaspiro[4.5]dec-3-enes, thereafter termed the “Bohlmann cyclisation.” This thesis describes the development of an analogous aza-Bohlmann cyclisation. Treatment of 2-(ω-aminoalkyl)furans with m-CPBA or singlet oxygen generates hydroxy- or methoxybutenolides, respectively, which undergo spirocyclisation upon treatment with H₂SO₄ to generate [4.4]- and [4.5]-spiroaminoacetals.

The axial/equatorial preferences of N-sulfonylspiroaminoacetals featuring a 3-O-isovaleryl or 3-O-benzyl substituent are described. Acid-catalysed equilibration revealed that in acetonitrile the axial isomer is thermodynamically favoured for both substrates.

The first total synthesis of the spiroaminoacetal alkaloid pandamarilactone-1 is discussed, via an aza-Bohlmann cyclisation, in 13 steps and 3% overall yield from 4-pentyn-1-ol.