Unusual heterocyclisation in the transformation of 6-halomethylsulfonyl-substituted bicyclo[3.1.1]heptane under Ramberg–Bäcklund reaction conditions

Васин, В. А.; Romanova, E. V.; Kostryukov, S. G.; Razin, V. V.

doi:10.1070/mc1998v008n03abeh000913

Cited by 8 publications

References 12 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

The Ramberg‐Bäcklund Reaction

Taylor

Casy

2003

Organic Reactions

View full text Add to dashboard Cite

The base‐mediated conversion of alpha‐halosulfones into region‐defined alkenes was first described by Ludwig Ramberg and Birger Backlund. This transformation has proved to be of wide synthetic value and is known as the Ramberg‐Backlund reaction (RBR). The facile nature of the RBR is surprising given the difficulties encountered when attempting to carry out nucleophilic substitution reactions on alpha‐halosulfones. In contrast to halogens adjacent to carbonyls and related electron‐withdrawing groups, polar, steric and field effects appear to combine leading to the marked deactivation of alpha‐halosulfones. The stereochemical outcome of the reaction was also unexpected: a predominance of Z‐alkenes is often observed with relatively weak bases, whereas stronger bases tend to favor E‐alkenes. The mechanism of the RBR was therefore the subject of intense interest, particularly in the 1950s and 1960s. From the synthetic viewpoint, the RBR is attractive for a number of reasons, for example, the accessibility of the precursor sulfide and sulfones; the conjunctive nature of the process; the unambiguous location of the resulting double bonds, among others. Organic sulfones are readily available, but the preparation of alpha‐halosulfones can be problematic. In view of this, perhaps the most significant synthetic advance concerning RBR has been the development of Meyer's modification, which involves in‐situ halogenation‐RBR sequence and enables sulfones to be converted directly into alkenes. This chapter discusses the mechanism of RBR, its scope and limitations, applications of the reaction in natural product synthesis, and comparison of the RBR with related procedures. Representative experimental procedures are also given.

show abstract

The Ramberg‐Bäcklund Reaction

Taylor

Casy

2003

Organic Reactions

View full text Add to dashboard Cite

show abstract

Ramberg‐Bäcklund Reaction

2010

Comprehensive Organic Name Reactions and Reagents

View full text Add to dashboard Cite

It is a base‐promoted transformation of α‐halosulfones into olefins with extrusion of SO 2 via an episulfone intermediate and is generally known as the Ramberg–Bäcklund reaction. This reaction is applicable for nearly all α‐halosulfones having at least one α‐hydrogen and occurs at very mild conditions. All the mechanistic features of the reaction have been discussed and the study is supported by the deuterium exchange experiment as well as the actual isolation of 2,3‐diphenylvinylenesulfone. It has been reported that the reaction occurs smoothly when exposed to a base, regardless of the number of α‐halogens. This reaction has been modified by the in situ chlorination of sulfone using CCl 4 and use of the KOH and Al 2 O 3 . This reaction has been applied in organic synthesis, especially for the preparation of natural products and C‐glycosides.

show abstract