Bi(III) Catalysed O-acylative cleavage of 2,5-dimethyltetrahydrofuran: a substrate dependent borderline mechanism |
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| Authors: | James F Costello William N Draffin Simon P Paver |
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| Institution: | Department of Chemistry, University of the West of England, Coldharbour Lane, Bristol BS16 1QY, UK |
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| Abstract: | The Bi(III) catalysed O-acylative cleavage of cis- and trans-2,5-dimethyltetrahydrofuran 4 with AcCl, BzCl or i-PrCOCl is stereochemically consistent with the operation of a concerted process (ANDN), which proceeds via a stabilised carbocation or ‘loose’ SN2 transition state. However, the O-acylative cleavage of cis-2,5-dimethyltetrahydrofuran 4 with sterically demanding electrophiles such as t-BuCOCl, appears to be stereochemically consistent with the alternative SN1 (DN+AN) pathway. The apparent merging of mechanistic pathways is rationalised by the participation of a strained acyloxy cation. |
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| Keywords: | Bi(III) Catalysis Cyclic ethers O-Acylative cleavage Borderline mechanism |
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