Tetrasubstituted tetrahydrofurans

We employed this reaction to stereoselectively synthesize 2,3,4,5-tetrasubstituted tetrahydrofuran compounds. Treating one major product (147a R = Ph, R" = Me) with LiN(SiMe3)2 selectively generates cis-eno-late anion A that condenses with aldehydes, presumably via a cyclic... 

A mild, efFident, Lewis acid-promoted addition of C3-substituted l,3-bis(silyl)propenes to aldehydes provides the corresponding 2,3,4, 5-tetrasubstituted tetrahydrofurans in excellent stereoselectivity (13TL3916). 

Epoxidation of the 1,2-double bond is followed by highly diastereoselective attack at the 5,6-double bond both oxirane rings in 372 can be opened separately under controlled conditions, forming the tetrasubstituted tetrahydrofurans 373 and 374 with very good overall yields . ... 

Acyltetrahydrofurans. These products can be obtained by BF3-catalyzed condensation of (Z)-4-hydroxy-l-alkenylcarbamates with aldehydes or ketones in high diastereo- and enantioselectivity.1 Use of a (Z)-anri-precursor (1) results in cis, trans, tram-tetrasubstituted tetrahydrofurans from aldehydes with high selectivity. 

The Lewis acid-promoted reaction of aldehydes with a-substituted allylsilanes forms 3-silyltetrahydrofurans in good to high yields.169-172 The use of homochiral allylsilanes is very valuable for highly diastereo- and enantio-selective syntheses of tri- and tetrasubstituted tetrahydrofurans (Equation (43)). Catalytic asymmetric [3-1-21-cycloaddition of a-substituted allenylsilanes to aldehydes can be achieved by a chiral scandium complex.173... 

In the total syntheses of 2,5-diaryl-3,4-dimethyltetrahydrofuran lignans (-f )-fragrasin (-f)-galbelgin, (-f)-talau-midin, (—)-saucernetin, and (—)-verrucosin, a novel ring closure to tetrasubstituted tetrahydrofurans by intramolecular attack on a quinoid intermediate has been described <2007SL475>. 

Cordia goetzei Giirke (stem bark) Bidihydrochalcones (tetrahydrofuro[3,2-cjbenzopyran and tetrasubstituted tetrahydrofuran derivatives) Cordigone (335) cordigol (323). Antifungal bichalcones. Marston et al., 1988[162]. 

Cyclization of homoallylic alcohols to tetrasubstituted tetrahydrofurans. This cyclization can be effected with almost complete stercocontrol by phenylsclcncnylation with Nicolaou s reagent 1. The products arc reduced with BujSnH/AIBN to trialkylated tetrahydrofurans. 

The addition of chiral ( )-crotylsilane to a- (and / -) alkoxy aldehydes provides a convenient route for the diastereoselective synthesis of tetrasubstituted tetrahydrofurans (Equation (102)) <91JA9868>. 

Scheme 4.5 Stereoselective synthesis of 2,3,3,5-tetrasubstituted tetrahydrofurans by domino Sfj2/Michel reaction.

C-Furanosyl compounds embody tetrasubstituted tetrahydrofurans which are analogs of naturally occurring furanosides, in which the anomeric oxygen has been replaced by a carbon atom, providing a non-labile ether functionality in place of the biochemically crucial acetal linkage. C-Furanosyl compounds occur widely in nature, and have been used as carbohydrate isosteres. We undertook preliminary molecular modelling studies on D-jylofuranosylethyne derivatives (Fig. 3), which we... 

Akindele T, Marsden SP, Gumming JG. Stereocontrolled assembly of tetrasubstituted tetrahydrofurans a concise synthesis of virgatusin. Org. Lett. 2005 7 3685-3688. 

This method can be applied to a variety of diazoesters in the presence of differently substituted silanes. Steric hindrance aroimd the silicon group does not interfere with the process. The allylsi-lanes obtained through this method were functionalized, for instance, through reduction of the ester function into an alcohol followed by an electrophilic 5-endo-tng cyclization, giving rise to a variety of tri- and tetrasubstituted tetrahydrofurans with high diastereocontrol (9). Panek et al. used these allylsilanes in Lewis acid—catalyzed crotylation processes with aldehydes to prepare highly functionalized vinylogous aldol products (10). 

The novel palladium-catalyzed [3 + 2] cycloaddition of trimethylene-methane with ketones provided access to highly enantioenriched tetrahydrofurans bearing a tetrasubstituted stereocenter with Cl-symmetric phosphoramidite (13AGE4466)... 

Trost and coworkers reported a novel palladium-catalyzed [3 + 2] cycloaddition of trimethylenemethane with ketones. This protocol provides access to highly enan-tioenriched tetrahydrofurans bearing a tetrasubstituted stereocenter (Scheme 2.4). In this process, the use of a Cl-symmetric phosphoramidite ligand is critical for establishing this reaction, which demonstrated a uniquely high activity under the reaction conditions [10]. 

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