Bromomethyl ß-styryl and ß-bromostyryl sulfones in the Michael-induced Ramberg-Bäcklund reaction

Condensation products of mono-and dibromo-substituted methyl vinyl sulfones with CH-acids enolates

“…The corresponding signal for compound 6b has an intermediate form: in the X part it appears as a triplet (virtual spin-spin coupling given in Table 4) and in the AB part it is more complex than a doublet, being a multiplet with one of the H-2 proton signals superimposed. _______ * 2 Part of this material has been reported in [7]. * 3 Assigned signals may be reversed.…”

“…Benzyl α-bromovinyl sulfone reacts with different nucleophiles by a similar scheme to give allyl derivatives [3]. As members of the series of α-bromovinyl bromomethyl and β-bromovinyl bromomethyl sulfones the dibromosulfones 2a and 3a also react via an MIRB reaction with sodium methylate, presumably through a bromomethyl ethynyl sulfone stage to form a vinyl phenyl ketone dimethyl ketal in both cases [2]. It is also known that some α-bromovinyl sulfones unable to take part in the Ramberg-Bäcklund reaction cyclize to sulfonyl-substituted aziridine derivatives when treated with primary amines in DMSO [4].…”

“…It was notable that the dibromosulfone 5b, which was obtained as a threo / erythro isomer mixture, gave exclusively on dehydrobromination the unsaturated sulfone 2b, the configuration of which was confirmed by reduction with zinc dust in acetic acid to the sulfone 1b. We have previously observed a similar reaction for the dibromosulfone 5a [2]. The CH-acids enolates were generated using NaH in THF at 20-45ºC under a dry argon atmosphere.…”

“…Detailed methods for the synthesis and proof of the structure of sulfones 1a-3a have been given by us in [2]. The sulfones 1b [2] and 3b [6] were identified from the constants and spectroscopic parameters reported in the literature.…”

“…The sulfones 1b [2] and 3b [6] were identified from the constants and spectroscopic parameters reported in the literature. It was notable that the dibromosulfone 5b, which was obtained as a threo / erythro isomer mixture, gave exclusively on dehydrobromination the unsaturated sulfone 2b, the configuration of which was confirmed by reduction with zinc dust in acetic acid to the sulfone 1b.…”