Domino Cyclization of 1,n-Enynes (n = 7, 8, 9) Giving Derivatives of Pyrane, Chromene, Fluorene, Phenanthrene and Dibenzo[7]annulene by Ruthenium Complexes.

Cyclization of the ether enyne 1 catalyzed by [Ru]NCCH3(+) ([Ru] = Cp(PPh3)2Ru) in CHCl3 generates a diastereomeric mixture of the substituted tetrahydropyran 11. Presumably, formation of an allenylidene complex is followed by a cyclization by nucleophilic addition of the olefinic group to Cγ of the ligand giving a boat-like six-membered ring. The diastereoselectivity is controlled by the 1,3-diaxial interaction. The vinylidene complex 7, a precursor of 11, is obtained from 1 and [Ru]Cl. In a mixture of MeOH/CHCl3, the domino cyclization of 1 further affords 14a, a chromene product catalytically. The second cyclization proceeds via nucleophilic addition of the resulting olefinic unit to Cα of 7. But the ether enyne 3 with a cyclopentyl ring on the olefinic unit undergoes only single cyclization due to steric effect. The propargyl alcohol and the two terminal methyl groups on the olefinic unit shape the cyclization. Thus, similar all-carbon 1,n-enynes (n = 7, 8, 9) 4-6 each with an aromatic linker undergo direct domino cyclization catalyzed by [Ru]NCCH3(+), to give derivatives of tricyclic fluorene, phenanthrene and dibenzo[7]annulene, respectively, with no intermediate observed.

Instantaneous room-temperature and highly enantioselective ArTi(O-i-Pr)3 additions to aldehydes.

Direct asymmetric additions of ArTi(O-i-Pr)(3) to aldehydes catalyzed by a titanium catalyst of (R)-H(8)-BINOL are reported. The reactions proceed instantaneously at room temperature, affording alcohols in ≥90% ee. Importantly, the ArTi(O-i-Pr)(3) reagent differentiates the ligand effectiveness in an order of H(8)-BINOL > BINOL > TADDOL > diol 3 > disulfonamide 2.

Highly enantioselective 3-furylation of ketones using (3-furyl)titanium nucleophile.

A novel asymmetric 3-furyl addition of (3-furyl)Ti(O(i)Pr)(3) to ketones in the presence of 10 mol % (S)-BINOL is reported. The catalytic system works excellently for aromatic ketones, alpha- or beta-halophenones, alpha,beta-unsaturated ketones, and acetylfuran, affording products in high yields with excellent enantioselectivities of up to 97% ee.

Triphen-yl(tetra-hydro-furan)-aluminium(III).

In the title compound, [Al(C(6)H(5))(3)(C(4)H(8)O)], the Al atom has a distorted tetra-hedral geometry. The C-Al-C angles range from 113.25 (7) to 116.27 (8)°, much larger than the O-Al-C angles, which range from 103.39 (7) to 103.90 (6)°. The tetra-hydro-furan ring adopts an envelope conformation. The crystal packing is stabilized by C-H⋯π inter-actions.