Ortho-quinone methides as reactive intermediates in asymmetric brønsted Acid catalyzed cycloadditions with unactivated alkenes by exclusive activation of the electrophile.

An efficient method for the highly enantioselective synthesis of chiral chromanes bearing multiple stereogenic centers was developed. A chiral BINOL-based N-triflylphosphoramide proved to be an effective catalyst for the in situ generation of ortho-quinone methides (o-QMs) and their subsequent cycloaddition reaction with unactivated alkenes provided chromanes with excellent diastereo- and enantioselectivity.

Experimental and computational study of the catalytic asymmetric 4π-electrocyclization of N-heterocycles.

The first asymmetric metal-catalyzed Nazarov cyclization of N-heterocycles has been developed. The use of a chiral catalyst allows the enantioselective electrocyclization of N-heterocycles under mild conditions and the corresponding products are obtained in good yields with excellent enantio- and diastereoselectivity. The reaction mechanism and the absolute configuration of the obtained products are explained by means of computational studies.

Combining rhodium and photoredox catalysis for C-H functionalizations of arenes: oxidative Heck reactions with visible light.

Direct, oxidative metal-catalyzed C-H functionalizations of arenes are important in synthetic organic chemistry. Often, (over-)stoichoimetric amounts of organic or inorganic oxidants have to be used in these reactions. The combination of rhodium and photoredox catalysis with visible light allows the direct C-H olefination of arenes. Small amounts (1 mol%) of a photoredox catalyst resulted in the efficient C-H functionalization of a broad range of substrates under mild conditions.

On the acidity and reactivity of highly effective chiral Brønsted acid catalysts: establishment of an acidity scale.

Stronger acid, higher speed: The pKa  values of a range of binol-derived Brønsted acids of three different types were measured and found to correlate directly with the catalytic properties of the acids: higher rate constants kI were observed for more acidic Brønsted acid catalysts (see plot; binol=1,1'-bi-2-naphthol).

Asymmetric Brønsted acid-catalyzed aza-Diels-Alder reaction of cyclic C-acylimines with cyclopentadiene.

A new chiral Brønsted acid-catalyzed aza-Diels-Alder reaction of cyclic C-acylimines with cyclopentadiene has been developed. The reaction provides optically active aza-tetracycles in good yields with high diastereo- and enantioselectivities under mild reaction conditions.

Asymmetric Brønsted acid-catalyzed nazarov cyclization of acyclic α-alkoxy dienones.

A Brønsted acid-catalyzed asymmetric Nazarov cyclization of acyclic α-alkoxy dienones has been developed. The reaction offers access to chiral cyclopentenones in a highly enantioselective manner. The reaction is complementary to our previously reported Brønsted acid-catalyzed electrocyclization reactions, which provided differently substituted optically active cyclopentenones with a fused tetrahydropyrane ring in good yields and with excellent enantioselectivities.

(1R,2S)-Methyl 1-(4-chloro-phen-yl)-3-oxo-1,2,3,4-tetra-hydro-cyclo-penta-[b]indole-2-carboxyl-ate 0.2-hydrate.

The title compound, C(19)H(14)ClNO(3)·0.2H(2)O, crystallizes with five mol-ecules and a disordered water mol-ecule in the asymmetric unit. Four of the five mol-ecules form hydrogen-bonded dimers via N-H⋯O hydrogen bonds towards another symmetry-independent mol-ecule, whereas the fifth mol-ecule forms a hydrogen-bonded dimer with its symmetry equivalent, also via N-H⋯O hydrogen bonds. The dihedral angle between the planes of the fused benzene ring and the five-membered ring to which it is attached is 79.45 (13), 49.00 (15), 72.49 (16), 81.91 (18) and 76.38 (16)° for the five mol-ecules in the asymmetric unit.