Enantiomerically pure 2,2-dibromocyclopropanecarboxylic acids, simple chiral building blocks

Preparative resolution of bromocyclopropylcarboxylic acids

“…10 Syntheses of acids rac-24j 20 and rac-19 31 were also previously reported. Physical and spectroscopic properties of chiral acids (+)-19 and (À)-19 6 as well as their methyl esters (+)-35 and (À)-35 18 were identical to those previously reported in the literature.…”

“…Successful known attempts at the resolution of halocyclopropylcarboxylic acids via the crystallization of diastereomeric salts include the use of (+)-dehydroabietylamine 20 (DHAA) 18,19 and brucine 20 for b-and a-BCCA, respectively. We have previously employed crystallization with (+)-DHAA in a scale-up preparation of both individual enantiomers of 2,2-dibromo-1-methylcyclopropanecarboxylic acid 19 in the synthesis of chiral cyclopropylphosphine ligands 21 (Scheme 5).…”

Stereo- and regiocontrol in ene-dimerisation and trimerisation of 1-trimethylsilyl-3-phenylcyclopropene

“…15 The main steps of the resolution process included: a) formation and separation of a diastereomeric salt 27, which was almost insoluble in common solvents and therefore wasn't subjected to recrystallization; b) recovery of enriched acid (þ)-26 (62% ee) from 27 and its subsequent further optical enrichment up to 89% ee by crystallization of racemic acid 26 from benzene/hexane mixture; c) the acid (-)-26 (10% ee) recovered from mother liquid was enriched to 91% ee analogously by precipitating of the parent racemate 26 from a benzene/hexane solution.…”

Chiral methyl trans-2,2-dichloro-3-methylcyclopropanecarboxylate upon exposure to thiophenolate nucleophile

“…[1][2][3][4][5][6][7][8][9][10][11] These compounds are excellent building blocks due to their availability in high enantiomeric purity, simple techniques of preparation, and a substantial synthetic potential of the cyclopropane ring. [12][13][14][15] For example, they were utilized in the asymmetric synthesis of pyrethroids 1,2 and other natural products, 3,4 stereoregular oligocyclopropanes, 5 chiral biaryls, 6 and liquid crystals. 7 In a recent article we efficiently resolved racemic trans-2,2-dichloro-3-methylcyclopropanecarboxylic acid into enantiomers 1.…”

“…Basic hydrolysis of the resulting mixture led to the acid (1R,3S)-5 containing the diastereomer (1S,3S)-5 as the main impurity. In the final step, acid (1R,3S)-5 was successfully separated from byproducts by a two-fold crystallization from CCl 4 .…”