Enantioselective organocatalytic aryloxylation of aldehydes with o-quinones

Organocatalyzed Asymmetric α-Oxidation, α-Aminoxylation and α-Amination of Carbonyl Compounds

“…The cycloadducts could be converted into the corresponding α-hydroxy esters by methanolysis followed by ceric ammonium nitrate (CAN) treatment. Similarly, α-unbranched aliphatic aldehydes reacted with o -chloranil or o -bromonil under organocatalysis to give the α-aryloxylated aldehydes in their hemiacetal form [ 129 ] ( Figure 35 ). The MacMillan type catalyst ( 44 ) provided superior results in aryloxylation of propionaldehyde (>70% yield and >80% ee ) than proline and its simple derivatives (36–53% yield, 33–40% ee ).…”

Organocatalytic oxa-Diels–Alder reaction of α,β-unsaturated ketones under non-classical conditions

“…Oxa-Diels-Alder reactions of ketone 1a with 4-(trifluoromethyl)benzaldehyde (2e), 4-chlorobenzaldehyde (2f) and 4-fluorobenzaldehyde (2g) in CH 2 Cl 2 at room temperature for 48 h did not proceed and only starting materials were isolated after these attempted reactions. Similarly, 4-fluorobenzaldehyde (2g) was inactive in the reaction with ketone 1b (Table 2, entries [15][16][17][18].…”

“…16 The oxa-DA reaction of orthoquinones and aldehydes afforded chiral benzo [1,4]dioxins. 17 The oxa-DA reaction of a-chloroaldehydes, as precursors of dienes, with a,b-unsaturated ketones was catalysed with chiral carbenes. 18,19 Carbenes also promoted oxa-DA reactions of ketenes with a,b-unsaturated ketones to give chiral lactones 20 or coumarins.…”

Organocatalytic Strategies for the Development of the Enantioselective Inverse‐electron‐demand Hetero‐Diels‐Alder Reaction

“…The reaction takes place in the presence of an imidazolidinone‐based catalyst and with moderate to good yields and enantioselectivities (Scheme 11 ). [19] In a similar way, Chen and coworkers described the enantioselective synthesis of hydroquinoxaline derivatives by means of an organocatalytic IEDHDAR. [20] …”