Bifunctionalized Allenes. Part XII. Electrophilic Cyclization and Addition Reactions of 4-Sulfinylated or 4-Sulfonylated Allenecarboxylates

GRAPHICAL ABSTRACT

Abstract

Reaction of 4-sulfinylated or 4-sulfonylated allenecarboxylates with different electrophilic reagents such as sulfuryl chloride, bromine, benzenesulfenyl, and benzeneselenenyl chlorides takes place with 5-endo-trig cyclization or 3,2-addition reaction depending on the kind of the substituent at the sulfur atom. Treatment of 4-(benzenesulfinyl)-allenoates with electrophiles gives 5-(benzenesulfinyl)-2,5-dihydrofuran-2-ones as a result of the neighboring carboxylate group participation in the cyclization. On the other hand, (3E)-4-(methansulfonyl)alk-3-enoates were prepared by chemo-, regio-, and stereoselective electrophilic addition to the C²‒C³-double bond in the allenoate moiety of 4-(methanesulfonyl)allenecarboxylates. When R¹ = Me, the treatment with electrophiles gives mixtures of (3E)-4-(methanesulfonyl)alk-3-enoates and (3E)-4-(methanesulfonyl)-2-methylenealk-3-enoates with ratios of about 1.6:1 as a result of addition and elimination reactions. A possible mechanism involving cyclization, addition, and elimination reactions of the 4-sulfinylated or 4-sulfonylated allenecarboxylates is proposed.

Keywords:

• 4-Sulfinylated allenoates
• 4-sulfonylated allenoates
• 2,5-dihydrofuran-2-ones
• neighboring group participation
• (3E)-3,2-adducts