Calcium-Promoted [3+3] Annulation of Morita-Baylis-Hillman Ketones with 2-Aminobenzothiazoles to Construct Pyrimidobenzothiazoles

The reaction of Morita-Baylis-Hillman (MBH) ketones with 2-aminobenzothiazoles is used to construct new analogues of 4H-benzo [4,5] thiazolo [3,2-a] pyrimidine. MBH ketone provides a desirable reactivity with significant outcomes. The mechanism of the reaction involves aza-Michael addition followed by intramolecular cyclization with the removal of a water molecule. This approach tolerates a wide range of substrate scope adequacy, using minimal loading of inexpensive and more abundant Ca(II) catalyst

Amano PS catalysed methanolysis of maleimides: An efficient synthesis of methyl maleanilates^†

1899-1901A first simple method for Amano PS catalysed methanolysis of maleimides 1a-f has been described to obtain methyl maleanilates 2a-f in 80-90% yields

Probing the Synergistic Catalytic Model: A Rationally Designed Urea-Tagged Proline Catalyst for the Direct Asymmetric Aldol Reaction

A urea tag was incorporated at the C-4 position of proline, <i>cis</i> to its COOH group, in order to explore the prospect of a synergistic effect between the two functional groups in the transition state of the enamine route to the asymmetric aldol reaction. The catalyst proved to be an excellent performer, delivering aldols in high yields and with excellent enantio- and diastereoselectivities using just 2 mol % loading in the presence of water; it also exhibited good levels of recyclability under aqueous conditions. The favorable results reveal the interesting possibility of an intramolecular host–guest interaction between the urea and the amino acid moieties, exerting a beneficial effect on catalysis. The concept could certainly offer a new direction toward more efficient catalyst design

Enantioselective enzymatic approach to (+)-and (-)-2-acetoxy/hydroxycyclopentanones

A new practical enzymatic approach to (+)- and (-)-2-acetoxy/hydroxycyclopentanones with 96-98% ee has been described via enzymatic hydrolysis of the meso-diacetate 2, Swern oxidation of the thus formed (±)-hydroxy acetates 3 and 4, followed by re-enzymatic resolution. Enantiomerically pure (+)- and (-)-2-hydroxycyclopentanones are in equilibrium with enediol 9 and slowly undergo racemisation, a process which could be arrested by protecting the hydroxyl group as the acetate