Partially saturated fluorinated heterocycles: diastereo- and enantioselective synthesis of β-trifluoromethyl-pyrroline carboxylates

Abstract

The first asymmetric synthesis of β-trifluoromethylated pyrroline carboxylates has been achieved by organocatalytic conjugated addition of adamantyl glycine imine to β-trifluoromethylated enones, followed by a deprotection/cyclization/dehydration sequence.

Cyclopentyl Methyl Ether: An Elective Ecofriendly Ethereal Solvent in Classical and Modern Organic Chemistry

“…N ‐3,5‐Bis( tert ‐butylbenzyl)cinchoninium bromide catalyzes the asymmetric 1,4‐addition of glycinate Schiff bases to 4,4,4‐trifluoro‐1‐arylbut‐2‐en‐1‐ones to afford, after treatment with concentrated HCl, β‐trifluoromethylated pyrrolines in good to very good yields with the same levels of enantio‐ and diastereoselectivities. Under the optimized conditions, CPME is a better solvent than toluene, mesitylene, CH 2 Cl 2 , Et 2 O, and THF (Scheme ) …”

“…Undert he optimized conditions, CPME is a betters olventt han toluene,m esitylene, CH 2 Cl 2 ,E t 2 O, and THF (Scheme 45). [84] Employing CPME as ar eaction medium, N-acylimidazoles react with tert-butyldimethylsilyl 2-(bromomethyl)phenyle ther in the presence of ac hiral triazolium pre-catalyst, CsF,1 8crown-6, and KOAc to afford av ariety of dihydrocoumarins enantioselectively (Scheme 46). [85] Undert he optimizedconditions, deprotonation of the precatalyst affords the corresponding N-heterocyclic carbene (NHC), which thereafter reacts with the N-acylimidazole to generate a nucleophilic NHC-enolate.…”

Catalytic Asymmetric Synthesis of Enantioenriched Heterocycles Bearing a CCF3 Stereogenic Center

“…and good enantioselectivities in the range of 72 to 88 % (Scheme 8). [35] Aiming at the incorporation of a CF 3 group intopyrrolines, other nucleophiles have also been surveyed in the initial asymmetric conjugate addition step. A small variation of using sterically demanding b,b-disubstituted enones 1 from the above two examples can potentially yield chiral CF 3 -pyrrolines that have an all-carbon quaternary stereocenter if carbonucleophiles are utilized.…”

ChemInform Abstract: Catalytic Asymmetric Synthesis of Enantioenriched Heterocycles Bearing a C—CF3 Stereogenic Center

“…and good enantioselectivities in the range of 72 to 88 %( Scheme 8). [35] Aiming at the incorporation of aC F 3 group intopyrrolines, other nucleophiles have also been surveyed in the initial asymmetric conjugate addition step. As mallv ariation of using sterically demanding b,b-disubstituted enones 1 from the above two examples can potentially yield chiral CF 3 -pyrrolines that have an all-carbon quaternary stereocenter if carbonucleophiles are utilized.…”