Anti-Selective Aldol Reactions of Pentafluorosulfanylacetic Acid Esters with Aldehydes Mediated by Dicyclohexylchloroborane

Abstract

Aldol reactions of pentafluorosulfanyl (SF5)-substituted acetic acid esters with both aromatic and aliphatic aldehydes proceeded with excellent anti-diastereoselectivity and good to high yields using dicyclohexylchloroborane/triethylamine. This methodology enabled the synthesis of hitherto unknown α-SF5-β-hydroxy esters. Using a norephedrine-based auxiliary, high asymmetric induction was observed. The stereochemistry of products was assigned by NMR spectroscopy and proved by X-ray diffraction analysis. The intermediate enolate was identified as a highly unstable species.

Catalytic Enantioselective Synthesis of Highly Functionalized Pentafluorosulfanylated Pyrrolidines

“…[11] Another approach, developed by Wang, relying on the Cu I -catalyzed 1,3-dipolar cycloaddition of azomethine ylides with 4,4,4-trifluorocrotonates, using aT F-Biphamphos or BTBM-Biphep-type catalyst, led to CF 3 -substituted pyrrolidines in very good yields and high levels of enantioselectivity (Scheme1,E q. As part of our research program dedicatedt ot he development of new methodologies to access pentafluoro-sulfanylated scaffolds, [15] we have reported the racemic synthesis of SF 5 -substituted pyrrolidines from SF 5 -subtituted acrylic esters or amides and azomethine ylides (Scheme 1, Eq. [12] Using as imilar approach,Z hang developed ac opper-catalyzed exo-selective [3+ +2] cycloaddition of azomethine ylides with b-CF 3 b,b-disubstitutede nones by using (S)-MeO-DTBM-Biphep as ac hiral catalyst (Scheme 1, Eq.…”

“…Quite surprisingly and despite the potential of this type of derivatives, the synthetic access to SF 5 ‐subtituted pyrrolidines remains scarce, and no asymmetric process has been reported to date. As part of our research program dedicated to the development of new methodologies to access pentafluoro‐sulfanylated scaffolds, we have reported the racemic synthesis of SF 5 ‐substituted pyrrolidines from SF 5 ‐subtituted acrylic esters or amides and azomethine ylides (Scheme 1, Eq. ()) .…”

Syn-selective silicon Mukaiyama-type aldol reactions of (pentafluoro-λ6-sulfanyl)acetic acid esters with aldehydes

“…1 ). Such an arrangement was found in the crystalline state of an anti -aldol product we obtained as a result of a boron-mediated aldol reaction of the benzyl ester analog of compound 1 with benzaldehyde [ 29 ]. This product and a couple of its aryl-substituted analogs exhibited coupling constants of 2.4–4.0 Hz.…”

“…A couple of years ago, we became interested in SF 5 -substituted ester enolates as reaction intermediates. Thus, in 2016 we reported a highly anti -selective aldol addition of SF 5 -substituted acetic ester-based boron enolates to aromatic and aliphatic aldehydes to form anti -2-pentafluoro-λ 6 -sulfanyl-3-hydroxyalkyl-carboxylic acid esters [ 29 ]. Quite similar results were published independently by Carreira et al a couple of weeks before us [ 30 ].…”

Chemoselective Hydro(Chloro)pentafluorosulfanylation of Diazo Compounds with Pentafluorosulfanyl Chloride

“… [7a,c, 17] Recently, Paquin developed a multistep synthesis of α‐SF 5 ketones starting from the addition of SF 5 Cl to alkynes (Scheme 2 d). [7f] These α‐SF 5 carbonyl compounds are valuable building block for further diversification [7c,d, 18] . To the best of our knowledge, there was only one example of the direct synthesis of α‐SF 5 carbonyl compounds from the addition of SF 5 Cl to ketene (Scheme 2 e).…”