Abstract:
Development of guanidine catalysts is explored through direct iminium chloride and
amine coupling, alongside a 2-chloro-l,3-dimethyl-IH-imidazol-:-3-ium chloride (DMC)
induced thiourea cyclization. Synthesized achiral catalyst N-(5Hdibenzo[
d,t][1,3]diazepin-6(7H)-ylidene)-3,5-bis(trifluoromethyl) aniline proved
unsuccessful towards O-acyl migrations, however successfully catalyzed the vinylogous
aldol reaction between dicbloro furanone and benzaldehyde. Incorporating chirality into
the guanidine catalyst utilizing a (R)-phenylalaninol auxiliary, generating (R)-2-((5Hdibenzo[
d,t] [1,3 ]diazepin-6(7H)-ylidene ) amino )-3 -phenylpropan-l-ol, demonstrated
enantioselectivity for a variety of adducts. Highest enantiomeric excess (ee) was afforded
between dibromofuranone and p-chlorobenzaldehyde, affording the syn conformation in
96% ee and the anti in 54% ee, with an overall yield of30%. Attempts to increase
asymmetric induction were focused on incorporation of axial chirality to the (R)phenylalaninol
catalyst using binaphthyl diamine. Incorporation of (S)-binaphthyl
exhibited destructive selectivity, whereas incorporation of (R)-binaphthyl demonstrated
no effects on enantioselectivity. Current studies are being directed towards identifying the
catalytic properties of asymmetric induction with further studies are being aimed towards
increasing enantioselectivity by increasing backbone steric bulk.
