Polysubstituted tetrahydrofuran

The synthesis of polysubstituted tetrahydrofurans was also achieved in a stereoselective manner by a formal [3+2] cycloaddition of an allylsilane with a-triethylsiloxy aldehydes. An example showing the mechanism is illustrated <02JA3608>. In another approach, allylsilane was also allowed to react with a-keto esters in a [3+2] annulation reaction, providing highly substituted tetrahydrofurans in good yields as single diastereomers <02OL2945>. 

The enantioselective total synthesis of the polysubstituted tetrahydrofuran (-)-citreoviral, the unnatural enantiomer, was synthesized by L.E. Overman et al. The Prins-pinacol rearrangement of an allylic 1,2-diol with an unsymmetrical ketone proceeded with high stereoselectivity. The jb/s(trimethylsilyl)-1,2-diol was condensed with the dimethyl acetal of the unsymmetrical ketone in the presence of catalytic amounts of TMSOTf, which yielded a nearly 1 1 mixture of the corresponding acetal and rearrangement product. The acetal was converted to the desired tetrahydrofuran product upon exposure to tin tetrachloride. 

The application of d5-2,3-disubstituted cyclopropane 1,1-diesters to [3 + 2]-annulations with aldehydes under the promotion of AICI3 can result in the formation of the desired polysubstituted tetrahydrofuran products... 

In 2005, Hilt and co-workers disclosed the facile intermolecular ring expansion of styrene oxide with several dienes, acrylates, enynes or styrenes under iron catalysis to afford polysubstituted tetrahydrofuran derivatives in a highly chemo- and regioselective fashion. The authors used FeCl2 mixed with a... 

The asymmetric reduction of y-phenylseleno ketones and the intramolecular substitution of the phenylselenone residue by the oxygen atom of a hydroxy group led to 2-substituted tetrahydrofurans (13OL3906). Polysubstituted furans were formed in the photoredox neutral coupling of alkynes with 2-bromo-1,3-dicarbonyl compounds. The reaction was carried out without any external stoichiometric oxidants (130L4884). 

In 2000, Fiirstner et al. reported platinum-catalyzed reaction of alkynyl allyl ethers 1 to tetrahydrofuran derivatives 2 (Scheme 27.1) [2]. After this pioneering work, the TT-acidic metal-catalyzed tandem carbon-heteroatom bond formation/1,3-migration reaction became a powerful synthetic method of polysubstituted heteroarenes, since the aromatization process often drives the migration of various carbon functional groups involving cleavage of a carbon-heteroatom bond. 

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