HYDROBORATION OF 1,1'-BI(CYCLOPENT-1-ENE) AND 3,3-BIINDENE:EXPERIMENTAL AND THEORETICAL STUDY

摘要

Hydroboration of bi(cyclopent-1-ene) (1) or 3,3'-biindene (2) with borane,thexylborane or (-)-isopinocampheylborane afforded,regardless of reaction conditions,meso-isomers of polycyclic 1,4-diols 3a,4a as the main products.No reaction was observed with 9-BBN.The structure of the major product 4a,as well as of the minor racemic product 4b was assigned based on ~1H NMR spectra of the corresponding Mosher's diesters 5a-5c.Finally,the stereochemistry of the product 4a was confirmed by a single-crystal X-ray analysis of the corresponding dimesylate 6.To elucidate preferential formation of the meso-isomers,complexes of monohydroborated intermediate with borane were studied theoretically by DFT methods.