Phosphine-Catalyzed Interrupted Morita-Baylis-Hillman Reaction and Switchable Domino Reactions of a-Substituted Activated Olefins with Formaldehyde and Mechanism Elucidation

Summary of main observation and conclusion 3-Olefinic oxindoles can undergo interrupted Morita-Baylis-Hillman reaction with formaldehyde. Apart from the previous reported dephosphoration to access reductive aldol-type products, here we uncovered that completely different pathways were followed by tuning the substitutions of 3-olefinic oxin doles. In com bin ation with formalin, an unexpected domino phosphorus-ylide formation, aldol-type addition, hemeacetal formation and O-substitution process was observed to produce 1,3-dioxolane derivatives. Moreover, a switchable sequence to produce formate derivatives via a key hydride transfer process was furnished by simply replacing formalin with paraformaldehyde. Density functional theory calculations were conducted to well elucidate the catalytic reaction mechanism.

Synthesis of cyclopentenyl and cyclohexenyl ketones via [3 + 2] and [4 + 2] annulations of 1,2-allenic ketones

In this paper, an efficient synthesis of cyclopentenyl ketones and cyclohexenyl ketones through tertiary phosphine catalyzed [3 ＋ 2] and [4 ＋ 2] annulations of 1,2-allenic ketones with activated alkenes has been developed. Compared with published synthetic methods on cyclopentenyl ketones and cyclohexenyl ketones, the protocols developed in this paper have the advantages such as readily available starting materials, mild reaction conditions and high efficiency.