Diels TADDOL catalysed

Narasaka and coworkers used the titanium complex of the TADDOL (a,a,a, a tetraaryl-l,3-dioxolane-4,5-dimethanol) ligand (8.50) to catalyse Diels-Alder reactions of acyloxazolidinones. Thus, the crotonyl derivative (8.51) was... 

The dienophile may also be activated by hydrogen bonding of the carbonyl oxygen with suitable protic molecules and it has been observed that Diels-Alder reactions are accelerated when performed in protic solvents such as 2-butanol. Thus the opportunity exists for the development of an enantioselective alcohol-catalysed asymmetric Diels-Alder reaction. Indeed, Rawal and coworkers have recently discovered that the use of catalytic amounts of the enantiomerically pure diol a,a,a, a -tetraaryl-l,3-dioxolane-4,5-dimethanol (TADDOL) (8.113) in the Diels-Alder reaction of aminosilyloxydiene (8.114) with 2-substituted acroleins such as (8.24), results in the formation of the cycloadduct (8.115) with high ee. Simiharly, the strong Bronsted acid (8.116) effectively catalyses the Diels-Alder reaction of sUyloxydienes such as (8.117) with a,P-enone (8.105). ... 

Table 7.4 Supported-TADDOL ligands in a titanium-catalysed Diels-Alder reaction.

In 2004 the same research group showed that TADDOLs 2 were able to catalyse other reactions via hydrogen-bonding activation, for example the Diels-Alder reaction between diene 1 and substituted acroleins 5 (Scheme 24.3), for this reaction 1-naphthyl-TADDOL 2a was the best catalyst. 

Scheme 24.2 Asymmetric hetero-Diels-Alder reaction catalysed by TADDOLs 2.

The Diels-Alder reactions of cyclopentadiene with vinyl ketones in water were favoured by high temperature at 1000 atm, owing to increasing entropy.A bioinspired triazacyclophane tridentate ligand (58) has been developed for the Cu(II)-catalysed Diels-Alder reaction in water. The new organocatalyst, 1-naphthyl-trani-a,a -(dimethyl-l,3-dioxolane, 5-diyl)bis(diphenyl methanol) (TADDOL)/Emim BF4,... 

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