Abstract
A straightforward procedure for the preparation of enantiopure phosphorothioates and diastereopure phosphorothioamidates of 2,2′,6,6′-biphenyltetrol is presented. Basic alcoholysis of compounds trans -3 and cis -3 proceeds in high diastereoselectivity to give only two of the six possible acyclic phosphorothioamidates 4a and 4b (or 5a and 5b). When diastereopure 4 and 5 are subjected to acid alcoholysis they lead to enantiopure cyclic phosphorothioates trans -6 and trans-7, respectively. All compounds prepared are solid, air stable and possess a C2 symmetry axis. Due to restricted rotation around the C1-C1′ bond, compounds 4a, 4b, 5a, 5b, 6 and 7 exist as stable atropisomers at rt. However for compounds trans-3 and cis-3, the bridged biphenyl system intercorverts at rt with a half-life of 6 h. The structure of compounds trans- 2,trans- 3, and 5a has been confirmed by X-ray analysis. Phosphorothioates and phosphorothioamidates can be tested as agrochemicals since these classes of compounds can inhibit acetylcholinesterase of many different insect species.
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