A highly chemo- and enantio-selective hetero-Diels–Alder reaction catalysed by chiral aluminium complexes

Abstract

A new, highly chemo-and enantio-selective catalytic hetero-Diels-Alder reaction of conjugated dienes containing allylic C-H bonds with carbonyl compounds has been developed; with the use of (9-(-)-BINOL-AlMe (BINOL = 1,l'-bi-2-naphthol) as a catalyst, simple conjugated dienes react with glyoxylate esters, giving the (R)-enantiomer of the hetero-Diels-Alder adduct as the major product with up to 97% ee.The hetero-Diels-Alder (HDA) reaction of conjugated dienes with carbonyl compounds is a fundamental reaction in organic chemistry.' The reaction of a conjugated diene having an allylic C-H bond with an electron deficient aldehyde can take two different reaction courses, leading to the formation of both the HDA product and the hetero-ene product [eqn. ( l)].'-' Great EWG = electron-withdrawing group

Catalytic Asymmetric Hetero-Diels–Alder Reactions of Carbonyl Compounds and Imines

“…However, the HDA adduct 7 a is the major product when a BINOL ± aluminum(iii) catalyst is applied. [14] The mechanism of the reaction of 5 a with 6 a leading to the ene adduct 8 is outlined in Scheme 4.…”

“…[28] The reaction of benzaldehyde 2 a with activated conjugated dienes such as 3 d was found to be catalyzed by [Eu(hfc) 3 ] (20) (hfc 3-(heptafluoropropylhydroxymethylene)camphorate) giving up to 58 % ee [Eq. (14)]. For other substrates the HDA adducts were obtained with 20 ± 40 % ee when the reaction was performed in CHCl 3 at room temperature with 1 mol % of 20.…”

“…[14] The reaction of ethyl glyoxylate (5 a) with simple dienes, such as 2,3-dimethyl-1,3-butadiene (6 a), in the presence of (R)-BINOL ± AlMe 12 g as the catalyst gives the HDA 7 a adduct as the major product in 73 % yield with up to 97 % ee and with only 7 % of the ene adduct 8 a [Eq. (15)].…”

Enantioselective Total Synthesis of Cyathin A3.

“…Aluminum BINOLate catalysts have been successfully employed in a variety of Diels-Alder reactions. 138,139 Although the catalyst prepared from 1:1 mixture of Me 3 Al and BINOL effectively promoted Diels-Alder reaction of 105 with 106, the enantioselectivety was modest.…”

Rigid and Sterically Regular Chiral 1,1′-Binaphthyl Polymers in Asymmetric Catalysis

“…The catalytic properties of (S)-8 are very similar to those of the monomeric 1,1'-bi-2-naphtholaluminum complex. [26] The zinc complex of polybinaphthyl (R)-9 can also catalyze the asymmetric epoxidation of a,b-unsaturated ketones in the presence of tBuOOH with up to 81 % ee as well as complete diastereoselectivity (Scheme 6). [27] In this case, the enantioselectivity of both the long linker polymer (R)-15 and monomer (R)-11 is much lower than that of (R)-9, indicating a positive cooperative effect between the adjacent binaphthyl units in (R)-9.…”