The Formation of Bridged Bicyclic 1,2,4-Trioxanes by Intramolecular Capture of β-Hydroperoxy Cations

✍ Scribed by Charles W. Jefford; France Favarger; Serenella Ferro; Daniel Chambaz; Alain Bringhen; Gerald Bernardinelli; John Boukouvalas

• Publisher: John Wiley and Sons
• Year: 1986
• Tongue: German
• Weight: 533 KB
• Volume: 69
• Category: Article
• ISSN: 0018-019X
• DOI: 10.1002/hlca.19860690735

✦ Synopsis

The 1 ,I-endoperoxide, prepared from 3-(4-methylnaphth-1 -yl)propanal by photo-oxygenation in CH2C12, gave on treatment with Ambrrlyst-15 m, 3,3,4a,pyran in 85% yield. Its structure was determined by X-ray crystal structure analysis. The 1,2,4-trioxane moiety is locked in a twist-boat conformation with wuns fusion to the parent six-membered ring. The 1,4-endoperoxides of the methyl, butyl, and phenyl ketone analogues of the aforementioned aldehyde underwent similar acid-catalyzed rearrangement to the corresponding bridged bicyclic trioxanes in 94,47, and 48 % yields, respectively.

Introduction. ~ We have recently shown that P-hydroperoxy cations 1, zwitterionic peroxides 2 and their structural equivalents can be captured in intermolecular fashion by aldehydes and ketones to give a wide variety of 1,2,4-trioxanes 3 [l]. The intramolecular version of these annelations has not been examined, although the crucial step of two recent syntheses of qinghaosu (4) did involve the internal construction of the trioxane ring [2] [3]. Apart from this specific example, the formation of bridged bicyclic 1,2,4-trioxanes is confined to serendipitous cases involving cycloaddition of singlet or triplet molecular oxygen to dienes and photoexcited quinones, respectively [4]. Consequently, 4 we decided to investigate the conditions for preparing bridged bicyclic 1,2,4-trioxanes. In this paper, we describe the intramolecular capture of P-hydroperoxy cations by suitably placed aldehyde and ketone groups. The molecules selected to produce such cations are the 1,4-endoperoxides of 3-(4-methylnaphth-l-yl)propanal and their methyl, butyl, and phenyl ketone analogues 14-17. Protonation is expected to generate the hydroperoxy allylic cations (e.g. 27) which will be available for capture by the pendent carbonyl function.