Issue 17, 2012

Conformational preferences of oxy-substituents in butenolide–tetrahydropyran spiroacetals and butenolide–piperidine spiro-N,O-acetals

Abstract

We describe the synthesis of a series of oxy-substituted butenolide spiroacetals and spiro-N,O-acetals by oxidative spirocyclisation of 2-[(4-hydroxy or 4-sulfonamido)butyl]furans. The axial–equatorial preference of each oxy-substituent is investigated (NMR) by an acid-catalysed thermodynamic relay of configuration between the spiro- and oxy-centres. The axial site is preferred for most oxy-substituents at synthetically useful levels. The potential origins of this preference are discussed in terms of a stabilising gauche effect combined with the influence of solvation. These results have relevance to the synthesis of bis(acetylenic)enol ether spiroacetals including AL-1 and related compounds.

Graphical abstract: Conformational preferences of oxy-substituents in butenolide–tetrahydropyran spiroacetals and butenolide–piperidine spiro-N,O-acetals

Supplementary files

Article information

Article type
Paper
Submitted
02 Nov 2011
Accepted
21 Feb 2012
First published
22 Feb 2012

Org. Biomol. Chem., 2012,10, 3506-3518

Conformational preferences of oxy-substituents in butenolide–tetrahydropyran spiroacetals and butenolide–piperidine spiro-N,O-acetals

S. Naud, S. J. Macnaughton, B. S. Dyson, D. J. Woollaston, J. W. P. Dallimore and J. Robertson, Org. Biomol. Chem., 2012, 10, 3506 DOI: 10.1039/C2OB06849D

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