Dearomative electrophilic spirocyclization via the intramolecular Ritter reaction: Diastereoselective access to hydrogenated spiroindolenines

Dearomative electrophilic spirocyclization based on the intramolecular Ritter reaction of (2-methoxyphenyl)cyclohexan-1-ols with thiocyanates allows the diastereoselective access to the novel hydrogenated spiroindolenines containing a 2,4-cyclohexadienone moiety. The scope and limitations of the reaction were examined. Alkyl thiocyanates and benzyl thiocyanate afforded spiroindolenines in moderate to good yields, whereas the use of β-oxothiocyanates was ineffective. The efficiency of the reaction was also highly dependent on the substitution patterns of the starting alcohols, including substituents on the α-position to the hydroxy group and the 2-methoxyphenyl moiety.