The synthesis and characterization of 3,3-disubstituted pent-4-enals and their 2,2-(trimethylenedithio)pent-4-enal precursors, including the X-ray crystal structure of (R)-3-ethyl-3-phenyl-2,2-(trimethylenedithio)pent-4-enal

Abstract

A variety of 3,3-disubstituted pent-4-enals (5a, R = Me, R′ = Et; 5b, R = Me, R′ = Ph; 5c, R = Et, R′ = Ph) has been prepared by the Raney nickel desulfurization of the corresponding 3,3-disubstituted 2,2-(trimethylenedithio)pent-4-enal precursors 4a–4c. The precursor compounds were prepared by the alkylation of 2-formyl-1,3-dithiane with the appropriate 3,3-disubstituted allylic bromide. The new compounds have been characterized by elemental analysis, infrared and nmr spectroscopy, and mass spectrometry. The crystal and molecular structure of (R)-4c has also been determined by X-ray crystallography. At temperatures of ca. 130 °C, compounds 4a–4c undergo intramolecular rearrangement to form the tri-substituted alkenes 6a–6c, which have also been characterized by the present study.