The first phosphine-catalyzed [4 + 2] annulation of γ-substituted allenoates with 2-arylidene-1H-indene-1,3(2H)-diones is disclosed. In the reaction, the γ-substituted allenoate serves as a new type of 1,4-dipolar synthon; this broadens the application of γ-substituted allenoates. This method also offers a powerful approach to the construction of highly substituted spiro[4.5]dec-6-ene skeletons in excellent yields, and with complete regioselectivity and high diastereoselectivity.

The highly enantioselective intermolecular cross Rauhut-Currier reaction of different active olefins catalyzed by a multifunctional chiral Lewis base was reported. The RC products were obtained in excellent yields (up to 98 %), high chemo- and enantioselectivity (up to 96 % ee). The reaction could be performed on a gram scale using 1 mol % of the multifunctional phosphine catalyst.

We have developed a novel strategy to control the product distribution between 2,3-dihydrofurans and biaryls from the same starting materials by tuning the catalytic or stoichiometric process. By controlling the loading of the phosphine PR 3 , the Morita-Baylis-Hillman carbonates can be selectively used as a C 1 or a C 3 synthon, respectively. This inves-tigation has given new insights into tunable domino reactions and will be useful in diversity-oriented synthesis (DOS).Scheme 1. Our work concerned with the phosphine-mediated domino reactions of Morita-Baylis-Hillman carbonates.

This feature article will describe the selected examples of organophosphine catalysis of γ-substituent allenoates with a wide range of electrophiles to give diverse annulations.