Cyclization Reactions of 2,3-Bis(phenylsulfonyl)-1,3-butadiene with Various Carbanions. A [4 + 1] Anionic Annulation Approach to Phenylsulfonyl-Substituted Cyclopentenes

Abstract

2,3-Bis(phenylsulfonyl)-l,3-butadiene undergoes conjugate addition in the presence of carbanions giving rise to a variety of unsaturated sulfones. Reaction with lithium enolates proceeds via an allylic anionic intermediate which undergoes a subsequent elimination of phenylsulfinate anion to produce an allene. Generation of enolates from silyl enol ethers results in conjugate addition to the diene without subsequent elimination. Substituted cyclopentenyl sulfones are available via a [4 + 1] annulation reaction of the diene with various distabilized carbanions. The reaction involves a tandem addition-proton exchange-addition sequence. In the special case of 2,4-pentanedione, pyrans are formed, the isomeric identity of which depends upon the reaction conditions. 2-Alkylated 1,3dicarbonyl compounds react with the activated diene to produce substituted allenes in high yield. Phenylsulfonyl alkenyl substituted allenes were conveniently prepared by a similar protocol and were found to serve as substrates for intramolecular [2+2] cycloaddition chemistry.

Synthesis of Saturated Heterocycles via Metal-Catalyzed Alkene Hydroamination or Hydroalkoxylation Reactions

“…Unsaturated carbon-carbon bonds in the form of allenes and alkynes are generally more reactive toward late transition metal-catalyzed hydrofunctionalization reactions, in part due to their higher energy π-electrons. The allene C═C π-bond is known to be~10 kcal/mol less stable than that of an alkene, leading to increased reactivity [79,80]. Intramolecular cyclizations of aminoalkynes and endo-cyclizations of allenes produce unsaturated heterocycles, whereas exo-cyclizations onto allenes in the presence of Lewis acidic metal complexes produce saturated 2-alkenyl-substituted heterocycles.…”

Regioselective addition reactions of 3-phenylsulfonyl-2-trifluoromethyl-1,3-butadiene with nucleophiles

“…Since the trifluoromethyl and sulfonyl group attached to 2-and 3-positions of the diene unit effects significant polarization of the double bond, this compound should be highly reactive toward nucleophilic addition because of its remarkably lowered LUMO energy level compared to 1,3-butadiene. Although nucleophilic addition reactions of doubly activated diene at the 2-and 3-positions have been well documented previously [26][27][28], there has been no report on the nucleophilic reaction of 3-phenylsulfonyl-2-trifluoromethyl-1,3-butadiene. Herein, we wish to report on the reactivity of 3-phenylsulfonyl-2-trifluoromethyl-1,3-butadiene toward the nucleophiles and its regioselectivity.…”

Synthesis and odour evaluation of allenic derivatives

“…Allenes are the simplest cumulenes (cumulated polyenes) with the general formula (R 1 )R 2 C=C=C(R 3 )R 4 . [1] The first reported synthesis of an allene dates back to 1887, [2] and the structure of such a functional group as well as that of other cumulenes was established earlier in 1874 by Van't Hoff.…”

“…[3] Lately, allenic compounds have regained considerable attention and allene chemistry has turned out to be a topic of high interest since their cumulative double bond structure has proven to exhibit particular physical and chemical properties. [4] Therefore, allenes have been involved in a plethora of recent organic transformations [5] and their preparation has been facilitated by the development of new synthetic strategies. [1,6] Allenes are interesting both as building blocks and as synthetic targets.…”