Modified Julia Fluoroolefination:  Selective Preparation of Fluoroalkenoates

Abstract

The modified Julia olefination reaction has been applied to develop a stereoselective synthesis of fluoroalkenoate derivatives from a fluorobenzothiazolyl sulfone and aldehydes or a ketone. The olefination reaction can be achieved by using a variety of bases. DBU and DBU in the presence of MgBr2 were found to be the most efficient systems to prepare either (Z)- or (E)-alkenoates in moderate to excellent stereoselectivity.

3,5‐Bis(trifluoromethyl)phenyl Sulfones for the Highly Stereoselective Julia–Kocienski Synthesis of α,β‐Unsaturated Esters and Weinreb Amides

“…Thus, in contrast to other proposed mechanisms, [24] the elimination of SO 2 and BTF-phenol is not a concerted process and does not occur in an anti fashion in our reaction system. The fact that a significant activation energy difference was computed in favour of TS2-syn over TS2-anti (∆∆G ‡ = 3.7 kcal/mol, ∆∆G ‡ DMF = 3.0 kcal/mol), leading to the formation of the experimentally encountered E isomer, suggests that TS2 is the selectivity-determining step of this reaction.…”

Highly Stereoselective Synthesis of Monofluoroalkenes from α‐Fluorosulfoximines and Nitrones

“…[4] One-step approaches, such as the Horner-Wadsworth-Emmons reaction, [5] Peterson olefination, [6] and Julia-Kocienski olefination, [7] have also been used to synthesize monofluoroalkenes; however, controlling the Z/E-stereoselectivity of monofluoroalkene products in these one-step reactions still remains a challenging task. [5][6][7] Herein, we report a highly efficient stereoselective synthesis of (Z)-monofluoroalkenes from an unprecedented reaction between a-fluorosulfoximines and nitrones.…”

“…[5][6][7] Herein, we report a highly efficient stereoselective synthesis of (Z)-monofluoroalkenes from an unprecedented reaction between a-fluorosulfoximines and nitrones.…”

Synthetic Utilization of 2‐Chloro‐1,1,1,2‐tetrafluoroethane

“…If other nucleophiles behave in a similar manner to the hydroxide ion Int-5 should accept further attack by a nucleophile after transformation to the corresponding acid fluoride (Scheme 3). This is actually the case, and addition of NaBH 4 , NaOMe, or BnNHLi readily furnished the corresponding allylic alcohol 9 b, [19] a,b-unsaturated ester 10 b, [19,20] and amide 11 b, respectively, in 70-79 % yield (Scheme 4).…”