Henry reaction tetrabutylammonium fluoride catalyst

The Henry reactions of A, ALdibenzyl-L-phenylalaninal with nitroalkanes using 1.2 equiv of tetrabutylammonium fluoride (TBAF) as the catalyst proceed in ahighly stereoselective manner, as shown in Eqs. 3.82 and 3.83. This reaction provides rapid and stereoselective access to important molecules containing 1,3-diamino-2-hydroxypropyl segments, which are cenhal structural subunit of the HIV protease inhibitor amprenavir (in Scheme 3.21). 

Finally, the most recent efforts of the Hong group provided the tetracyclic scaffold of steroids in a two-component, three-step Michael/Michael/aldol/Henry cascade (Scheme 14.8c) [19]. The preferred catalyst ent)-ll, however, could not deliver the high diastereoselectivity that was obtained in the previous syntheses (56 44 dr). The excellent enantiomeric excess (98/99% ee), on the other hand, encouraged further development of the cascade (Scheme 14.8c). After the Michael/Michael sequence, the medium was acidified to complete the Robinson annulation to enone 64. Interestingly, subsequent treatment with only 0.5 equiv of tetrabutylammonium fluoride (TBAF) effected a very fast reaction to the target tetracycle (63%) at low temperature. 

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