Morita BINOL-catalyzed

Table 6.32 BINOL-catalyzed Morita-Baylis-Hillman reactions of cyclic enones.

The aza-Morita-Baylis-HiUman reaction is known to be a useful and atom-economical C-C bond-forming reaction of electron-deficient alkenes with imines usually catalyzed by Lewis bases [202]. It formally involves a sequence of reactions including a Michael addition, a Mannich reaction, a proton transfer, and a retro-Michael reaction ( -elimination). Although there are many reports in the field of the enantioselective aza-Morita-Baylis-Hilhnan reaction, only rare examples of asymmetric domino reactions initiated by this reaction have been reported. In 2010, Sasai et al. [203] developed the first organocatalyzed asymmetric domino aza-Morita-Baylis-Hillman/aza-Michael reaction of a,p-unsaturated carbonyl compounds with N-tosylimines, allowing an easy access to chiral cis-1,3-disubstituted isoindolines as single diastereomers. The process was induced by a Hg-BINOL-derived catalyst and provided these products in high yields and enantioselectivities, as shown in Scheme 10.18. 

Schaus and coworkers have developed a general route to the Clerodane diter-pene core by the use of previously developed B rousted acid catalyzed asymmetric Morita-Baylis-Hillman (MBH) reaction/Lewis acid mediated ring-annulation process (Scheme 1.33) [31]. Excellent diastereoselectivity was achieved in the key MBH reaction in the presence of 10mol% of the chiral BINOL derivative (29), affording the key intermediate for the synthesis of Clerodane decalin core. 

The ability of chiral binaphthol (BINOL) derivatives as a Br0nsted acid catalyst to facilitate asymmetric transformations was demonstrated by Schaus by the development of the highly enantioselective Morita-Baylis-Hilhnan reaction of cyclohex-enone with aldehydes effectively catalyzed by (R)-octahydro-l,l -bi-2-naphthol derivatives, bearing either 3,5-bis(trifluoromethyl)phenyl (24a) or 3,5-xylyl (24b) groups at the 3,3 -positions, in combined use with triethylphosphine as a nucleophilic promoter (Scheme 7.43) [68]. 

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