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Title: The Aza-Bohlmann cyclisation and the synthesis of Pandanus alkaloids
Author: Macnaughton, Sarah
ISNI:       0000 0004 2728 148X
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 2011
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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.
Supervisor: Robertson, Jeremy ; Dallimore, Jonathan Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Natural products ; Organic synthesis ; Organic chemistry ; Heterocyclic chemistry ; Furan ; spiroaminal ; spiroaminoacetal ; oxidative spirocyclisation