Ullmann dimerization of substituted methyl 3-X-1-benzothiophene-2-carboxylates 1-7 (X = Cl, Br) gave rise to the corresponding dimeric 3,3'-bi(1-benzothiophene) esters 8-13. Resolution of the title acid 20 by fractional crystallization of its mono- and bisquininium salt afforded pure (R)- and (S)-enantiomers, the optical purity and absolute configuration of which was confirmed by CD spectrometry and by X-ray crystallography. Ullmann dimerization of chiral oxazolines 23 and 24 derived from 2 proceeded without any diastereodifferentiation. Reduction of (R)- and (S)-20 afforded the corresponding (R)- and (S)-diols 29, which served as chiral ligands in a model enantioselective reduction of acetophenone. (R)- and (S)-1-phenylethan-1-ol were formed in 28 and 29% e.e., respectively.
用替代基取代的甲基3-X-1-苯并噻吩-2-羧酸甲酯(X = Cl,Br)进行Ullmann二聚化反应,得到相应的二聯苯并噻吩酯(8-13)。通过对标题酸20进行单酰铵盐和双酰铵盐的分馏结晶,得到纯度较高的(R)-和(S)-对映体,其光学纯度和绝对构型通过CD光谱和X射线晶体学得到确认。从2衍生的手性噁唑啉23和24的Ullmann二聚化反应在没有差向异构化的情况下进行。对(R)-和(S)-20的还原得到相应的(R)-和(S)-二醇29,它们在模型对苯甲酮的对映选择性还原中作为手性配体。分别形成28%和29%的(R)-和(S)-1-苯基乙醇。