Reactions of cumulated and conjugated dienes with sulfur trioxide

✍ Scribed by Ruud M. Schonk; Bert H. Bakker; Hans Cerfontain

• Publisher: Elsevier Science
• Year: 2010
• Tongue: English
• Weight: 652 KB
• Volume: 112
• Category: Article
• ISSN: 0165-0513
• DOI: 10.1002/recl.19931120301

✦ Synopsis

Abstract

The reactions of a series of cumulated (1a‐5a) and conjugated alkadienes (8a‐13a) with sulfur trioxide have been studied in the temperature range of −60 to 25°C using dichloromethane as solvent and 1.5 equiv of dioxane as reactivity moderator. Reaction of tetramethylallene (1a) at low temperature yielded the β‐sultone 1b, which at 0°C was slowly converted into 2,4‐dimethyl‐1,3‐pentadiene‐3‐sulfonic acid (1f). This conjugated dienesulfonic acid, in the presence of additional SO~3~, at 0°C, was rapidly converted into the unsaturated δ‐sultone 1g. Reaction of 1,2‐ cyclononadiene (5a) with SO~3~, formed an exception to the generally observed formation of the unsaturated δ‐sultones g, as at low temperatures a 1:1 mixture of 2‐cyclononene‐2,1‐sultone (5b) and the corresponding carbyl sulfate (5d) was formed. These products at 0°C were both converted into the same alkadienesulfonic acid, viz. 6. Upon using an excess of SO~3~, 6 was rapidly converted into 3‐cyclononene‐1,2‐sultone‐3‐sulfonic acid (7).

Reaction of the conjugated alkadienes 8a‐13a with sulfur trioxide led to the formation of the similar unsaturated δ‐sultones 8g‐13g, as observed upon starting with the cumulated dienes 1a‐5a. The reactions of SO~3~ with the conjugated alkadienes 9a‐12a clearly demonstrate that the formation of the δ‐sultones proceeds non‐stereospecifically. The formation of the unsaturated δ‐sultones from the alkadienes 1a‐5a and 8a‐13a is, therefore, suggested to proceed via a two‐step reaction, viz. An initial [2__s__ + 2__s__] cycloaddition, followed by very fast conversion of the resulting β‐sultone into the unsaturated δ‐sultone g.