Asymmetric cyclization reactions of allenoates with imines or α,ß-unsaturated ketones catalyzed by organocatalysts derived from cinchona alkaloids.

Lewis base-catalyzed cyclization reactions of allenoates with electron-deficient olefins and imines have been demonstrated by the preparation of biologically active natural products and pharmaceutically interesting substances and have emerged as powerful synthetic tools in the rapid construction of cyclic molecular complexity. In contrast to phosphine-containing Lewis bases, nitrogen-containing Lewis base amines display markedly different reaction profiles; however, this area is not well-developed. Herein we summarize the recent progress in this emerging field and outline the challenges ahead.

DABCO-catalyzed regioselective cyclization reactions of ß,γ-unsaturated α-ketophosphonates or ß,γ-unsaturated α-ketoesters with allenic esters.

Highly efficient DABCO-catalyzed [4 + 2] cycloaddition of ß,γ-unsaturated α-ketophosphonates or ß,γ-unsaturated α-ketoesters with allenic esters gives the corresponding highly functionalized tetrahydropyran and dihydropyran derivatives in good to excellent yields and moderate to good regioselectivities under mild conditions.

Synthesis of optically active dihydropyrans from asymmetric [4 + 2] cycloaddition of ß,γ-unsaturated α-ketoesters with allenic esters.

ß-Isocupreidine (ß-ICD) catalyzed asymmetric [4 + 2] cycloaddition of ß,γ-unsaturated α-ketoesters with allenic esters afforded ester-substituted functionalized dihydropyran derivatives in high yields along with high enantioselectivities under mild conditions.

Enantioselective synthesis of highly functionalized phosphonate-substituted pyrans or dihydropyrans through asymmetric [4+2] cycloaddition of ß,γ-unsaturated α-ketophosphonates with allenic esters.

Tell me which you want: catalytic asymmetric [4+2] cycloadditions of ß,γ-unsaturated α-ketophosphonates with allenic esters catalyzed by organocatalysts derived from different cinchona alkaloids have been developed, affording phosphonate-substituted functionalized pyran and dihydropyran derivatives in excellent yields with high enantioselectivities under mild conditions. The choice of product is controlled by the hydrogen bonding characteristics of the chosen catalyst.

Multifunctional chiral phosphines-catalyzed highly diastereoselective and enantioselective substitution of Morita-Baylis-Hillman adducts with oxazolones.

Multifunctional chiral phosphine (phosphine-thiourea type) L2-catalyzed allylic substitutions of MBH adducts 1 with oxazolones 2 produce the corresponding optically active adducts 3 in good to excellent yields and ee's as well as moderate to good de's under mild conditions. The synergistic interaction between hydrogen bond donor site and nucleophilic site has been discussed, indicating that finely tuning the active sites of the multifunctional phosphine organocatalysts is very important.