Metal Triflate-Promoted Allylic Substitution Reactions of Cinnamyl Alcohol in the Presence of Orthoesters and Acetals

Abstract

The product distribution of ethers formed from the reaction of cinnamyl alcohol with orthoesters in the presence of indium (III) triflate (InOTf)3 is dependent on both the reaction temperature and catalyst loading. Carrying out the reaction at room temperature under low loadings of the catalyst leads to a facile reaction generating the unexpected secondary allyl ether as the major product. In contrast, carrying out the reaction under higher catalyst loadings at elevated temperatures provides the expected primary linear ether in high yield and with excellent selectivity. The etherification reaction is also effective in the presence of acetals and ketals in place of orthoesters and allows for the development of the procedure to encompass a telescoped etherification protocol in which the acetal is generated in situ.

Indium Triflate's Transformative Role in Modern Organic Synthesis: A Five‐Year Survey of Functionalization, Cyclization, and Multicomponent Reactions

“…The nucleophilic attack of the zwitterionic 1,4-dipole intermediates on DMM may then start the annulation, which was similar to the suggested one in the [4 + 2] cyclization of D-A to form cyclohexane (8) product (Scheme 5). [14] Using indium triflate [In(OTf) 3 ] as a catalyst, Saikia's group (in 2020) developed a one-pot tandem reaction to synthesize substituted tetrahydropyrroloisoindolone (24) in moderate to good yields. The reaction involved N-propargyl amido alcohols (22) with 1,3-dicarbonyl compounds (23) via Mannich reaction followed by a Conia-ene cyclization reaction.…”

“…It is also possible to develop the technique to include a telescoped etherification protocol in which the acetal is created in situ since the etherification reaction is effective when acetals and ketals are present instead of orthoesters (Scheme 15). [24] …”

“…It is also possible to develop the technique to include a telescoped etherification protocol in which the acetal is created in situ since the etherification reaction is effective when acetals and ketals are present instead of orthoesters (Scheme 15). [24] Hajra et al, (2019) investigated an effective approach to synthesize C(3)À N(1') bisindoles by adjusting the nucleophilicity of indoline to that of spiro-epoxyoxindole. This was achieved by carefully adjusting the nucleophilicity of indoline towards spiroepoxyoxindole.…”