Functionalization of [2.2]Paracyclophanes via a Reductive Sulfanylation Reaction

Abstract

An expeditious route to planar chiral sulfur-based scaffolds has been achieved in two operational steps from cheap and commercial [2.2]paracyclophane hydrocarbon. The sulfur atom was introduced in a specific benzylic position of the [2.2]paracyclophane according to a reductive sulfanylation reaction, which proceeds under two complementary reaction conditions with either the BF3•OEt2/Et3SiH or TFA/BH3 . THF combinations. The study was completed by the development on a highly efficient resolution approach by HPLC.

Compact CPL emitters based on a [2.2]paracyclophane scaffold: recent developments and future perspectives

“…Although quite expensive, chiral HPLC on semi-preparative or preparative scales is frequently employed in paracyclophane chemistry as a useful way to access a variety of enantiopure products. [41][42][43][44][45][46][47][48][49] To-date, this technique remains a method of choice for the late-stage separation of complex pCp molecules. Chemical processes constitute a valuable alternative to access optically active pCps in an efficient, more economical fashion.…”

Enantiopure planar chiral [2.2]paracyclophanes: Synthesis and applications in asymmetric organocatalysis

“…HPLC on semi-preparative or preparative scales can also be employed as an effective way to separate the two enantiomers of racemic mixtures. Although costly, this approach has been extensively applied in paracyclophane chemistry to access a variety of enantiopure products, such as pCp-based acids (for a selected example, see Lämmehofer et al 25 ), anilines (for a selected example, see Meyer-Eppler et al 26 ), imines or hydrazones (for a selected example, see Masterson et al 27 ), and sulfur-containing compounds (for a selected example, see Deschamps et al 28 ) among many others. [29][30][31][32][33] Moreover, even if it is not always easy to implement, preparative chiral HPLC today remains a method of choice for the late-stage separation of complex pCp molecules (for a selected example, see Hasegawa et al 34 ).…”

Synthesis of [2.2]Paracyclophane‐Based Glycidic Amides Using Chiral Ammonium Ylides

“…[16][17][18][19][20][21][22][23][24][25][26] Utilizing them as starting materials either in racemic or enantioenriched form provides access to unique chiral ligands and organocatalysts, as well as more advanced novel PCP derivatives that may show interesting properties (on a longer term perspective). [3,10,[16][17][18][19][20][21][22][23][24][25][26] Importantly, racemic 4-formyl [2.2]paracyclophane 2, [13][14][15] as well as different diformyl [2.2]paracyclophanes, [19] can easily be obtained from 1 and, given their high synthetic value, it comes as no surprise that the development of robust enantioselective (resolution) approaches to access enantioenriched formyl-containing PCPs has attracted considerable attention over the last decades. [16,17,[20][21][22][23][24] As already state above, these compounds, i. e. 4formyl[2.2]paracyclophane 2 (Scheme 1,A), have been utilized for numerous further manipulations.…”

“…Monoformyl and diformyl‐substituted PCPs have been known for decades [13–15] and are amongst the most frequently employed PCP building blocks [16–26] . Utilizing them as starting materials either in racemic or enantioenriched form provides access to unique chiral ligands and organocatalysts, as well as more advanced novel PCP derivatives that may show interesting properties (on a longer term perspective) [3,10,16–26] .…”

“…Monoformyl and diformyl‐substituted PCPs have been known for decades [13–15] and are amongst the most frequently employed PCP building blocks [16–26] . Utilizing them as starting materials either in racemic or enantioenriched form provides access to unique chiral ligands and organocatalysts, as well as more advanced novel PCP derivatives that may show interesting properties (on a longer term perspective) [3,10,16–26] . Importantly, racemic 4‐formyl[2.2]paracyclophane 2 , [13–15] as well as different diformyl[2.2]paracyclophanes, [19] can easily be obtained from 1 and, given their high synthetic value, it comes as no surprise that the development of robust enantioselective (resolution) approaches to access enantioenriched formyl‐containing PCPs has attracted considerable attention over the last decades [16,17,20–24] …”