Biaryl dimethanols

A simple, commercially available chiral alcohol, a,a,a a -tetraaryl-l,3-dioxo-lane-4,5-dimethanol (TADDOL, 7a), catalyzes the hetero- and carbo-Diels-Alder reactions of aminosiloxydienes with aldehydes and a-substituted acroleins to afford the dihydropyrones and cyclohexenones, respectively, in good yields and high enan-tioselectivities. More recently, it was reported that axially chiral biaryl diols 7b and 7c were more highly effective catalysts for enantioselective hetero-Diels-Alder reactions (Scheme 12.5). ... 

Yamamoto and Rawal developed a novel axially chiral l,l -biaryl-2,2 -dimethanol (BAMOL) scaffold (32) (Figure 2.28) as a catalyst for the hetero Diels-Alder... 

Rawal and Yamamoto visualized that axially chiral l,l -biaryl-2,2 -dimethanols (BAMOLs) 25a and 25b possessing the 4-fluoro-3,5-dimethylphenyl and 4-fluoro-3,5-diethylphenyl groups, respectively, could activate the aldehyde carbonyl through hydrogen bonding and thus act as a prominent catalyst for the enantiose-lective hetero-Diels-Alder reaction of an aminosiloxydiene with a wide variety of aldehydes as illustrated in Scheme 7.44 [69]. 

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