The Optical Activity of Butylethylhexylpropylmethane¹

Four Decades of the Chemistry of Planar Hypercoordinate Compounds

“…With such building blocks, simple molecules (25 a-c)a sw ell as elaborate aromatic and 5 ]molecules. [60] The bond lengths are given in .…”

Synthesis and Stereochemical Assignment of Crypto‐Optically Active 2H6‐Neopentane

“…[1] However,i ns ome very special cases of chirality,d ue to the electronic properties of the chiral molecule,t he optical rotation is not measurable. [2] Thed etermination of the absolute configuration of these cryptochiral [3] -better called crypto-optically active [4] -compounds remains therefore extremely challenging.F or instance,asuitable prototype of acrypto-optically active molecule is appropriately deuterated neopentane (excluding its carbon isotopologues), C(CH 3 …”

“…[17] Due to the high sensitivity of the quadrupolar interaction (H Q )t os mall variations of ordering of the C-D vector, the method is particularly efficient in discriminating between enantiomers of chiral molecules (isotopically enriched or at natural-abundance deuterium level), including compounds that are chiral by virtue of isotopic substitution such as 2. [18][19][20] Thepresence of two quadrupolar doublets (j Dn Q j= 8a nd 15 Hz) in the 2 H-{ 1 H} spectrum of (AE)-2 H 3 -2 recorded in the CLC shows that spectral discrimination does occur ( Figure 1A,top);the determination of peak surfaces performed by deconvoluting the 2 Hs ignals in the enantioenriched series indicate that the enantiomeric ratio is higher than 98:2 ( Figure 1A,b ottom). When (S)-2 H 3 -2 is treated with the Negishi reagent, [21] the combined zirconocene-mediated allylic C À Hbond activation followed by selective C À Cb ond cleavage and deuteration of the resulting bismetalated species with 2 H 3 O + gives (R)-2 H 5 -3 on gram scale in 91 %y ield.…”

“…As the stereogenic quaternary center is at no risk of racemization in the process,the optical purity is identical throughout the rest of the synthesis (Scheme 1). Subsequent oxidative cleavage of the double bond followed by the in situ reduction with NaBD 4 leads to the volatile neopentanol which must be protected in situ to give the tosylate adduct (R [ 16] Thestructure of 2 H 6 -1 was definitively established by 2 HNMR spectroscopy with and without proton decoupling in an isotropic solvent ( Figure 1B,top and bottom). Thus,the presence of three 2 1 Hd ecoupling is turned off (see also the Supporting Information).…”

“…Subsequent oxidative cleavage of the double bond followed by the in situ reduction with NaBD 4 leads to the volatile neopentanol which must be protected in situ to give the tosylate adduct (R [ 16] Thestructure of 2 H 6 -1 was definitively established by 2 HNMR spectroscopy with and without proton decoupling in an isotropic solvent ( Figure 1B,top and bottom). Thus,the presence of three 2 1 Hd ecoupling is turned off (see also the Supporting Information). Considering the positive results for the determination of the enantiomeric ratio of (S)-2 H 3 -2,and previous studies on isotopic enantiodiscrimination, [19]2 H-{ 1 H} NMR in PBLG mesophases,w eapplied the same technique again to differentiate the enantiomeric signals of (rac)-2 H 6 -1, with the goal of assessing the enantiopurity of enantioenriched (S)-2 H 6 -1.I nterestingly,s mall but spectrally resolved quadrupolar doublets (j Dn Q j< 2Hz) associated with the mono-and dideuterated methyl groups (see the Supporting Information) indicate that this asymmetric (C 1 point group) molecule is slightly oriented in this weakly aligning lyotropic chiral mesophase.Unfortunately,all attempts to discriminate the enantiomers based on RQC differences failed, irrespective of the temperature (in arange of 30 K) and the polarity of the cosolvent (CHCl 3 or pyridine).…”