Trimethylsilyloxyfuran

(a) Natsume, M. Muratake, H., Tetrahedron Lett. 1979,3477. (b) Conde-Frieboes, K. Hoppe, D., Synlett 1990,99. 

Physical Data bp 44—46 °C/17 ininHg d 0.93 g mL . Solubility sol most organic solvents, e.g. CH2CI2, Et20, benzene, THE, MeCN. 

Form Supplied in colorless liquid commercially available (98% pure) but expensive. 

A list of General Abbreviations appears on the front Eru apers 

Preparative Method accessible by silylation of 2(5//)-fura-none, wbicb is obtained at very low cost by oxidation of furfural. 

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Methoxy-2-trimethylsilyloxyfuran is also a highly efficient diene under the influence of Lewis acids this compound is substituted readily at position 5 with a wide variety of agents (Scheme 74) (82TL353). 

Dihydro-2,5-dimethoxyfuran 824 reacts neat at 24°C with TCS 14 via the intermediate 825, the 2-trimethylsilyloxyfuran 826 (which can also be readily prepared from 5H-furan-2-one), and 827-829 to give the crystalline trimer 830 in 20% yield [21]. In the presence of aldehydes such as thiophen-2-aldehyde 831a or benzaldehyde 831b, however, 824 reacts via 832 to give the condensation products 833 a and 833 b, which are obtained in 30 and 62% yield, respectively [22, 23] (Scheme 6.11). Because it is postulated 2-trimethylsilyloxyfuran 826 is a intermedi-... 

Likewise, addition of enol silyl ethers such as 980 to the intermediate 977 a furnish the 5-trimethylsilylmethylisoxazolidine 981 in 61% yield and 15% isoxazoline 982 [73, 74] whereas addition of 2-trimethylsilyloxyfuran 827 to 977 a affords, via the intermediates 983, on work-up with CF3CO2H, 96% yield of a mixture of lactones 984 and 985 [75] (Scheme 7.23). More recently it has also been reported that Danishefsky (trimethylsilyloxy)dienes add to intermediates such as 977 to give the corresponding products [76]. 

Trimethylsilyloxyfurans were employed as C5-dianion equivalents in the spiroannulation with bi-functional ortho-esters to provide spirobutenolide derivatives <060L3705>. When the second step was performed under radical conditions, instead of using base, r is-fused bicyclo[3.n.0]lactones were formed <06CC1200>. An interesting example is... 

Triisopropylsilyloxyfurans were effective nucleophiles for the vinylogous Mannich addition to iminium ions that were formed by Rh2(cap)4-catalyzed oxidation of N-alkyl groups by THYDRO <06JA5648>. A stereoselective addition of 2-trimethylsilyloxyfurans to aryl aldehydes-derived aldimines employing a chiral phosphine/Ag complex as catalyst was developed <06AG(I)7230>. The prototypical example is shown below. 

L2909>. An organocatalytic addition of 2-trimethylsilyloxyfuran to aldehydes using 10 mol% of l,3-bis(3-(trifluoromethyl)phenyl)urea provided adducts with modest threo selectivity <06TL8507>. A syn-selective, enantioselective, organocatalytic vinylogous Mukaiyama-Michael addition of 2-trimethylsilyloxyfuran to (E)-3-... 

Scheme 6.32 y-Butenolides obtained from diastereoselective aldol addition of 2-trimethylsilyloxyfuran to aldehydes catalyzed by urea 32. 

Trimethylsilyloxyfuran (274) reacts with ethoxycarbonylnitrene to give 3-ethoxycarbonyl-3,4-dihydro-l,3-oxazin-2-one (276) via aziridine intermediate (275) (89TL5025). 

Racemic tandem additions Mild carbon nucleophiles add to the [Os]-anisolium complex 27 exclusively at C3 to afford substituted 1,3-cydohexadiene complexes 29-32 in moderate to high yields (Table 8) [21]. Nucleophiles that have been utilized in this manner include MMTP (29 and 30), N-methylpyrrole (31), and 2-trimethylsilyloxyfuran (32). As with other tandem additions to [Os] complexes, both the nucleophile and the electrophile add to the arene face opposite to that involved in metal coordination, such that the products are those of syn addition. 

The bicyclic isoxazolidine 76 was prepared by nucleophilic addition of 2-trimethylsilyloxyfuran to A-gulosyl-nitrones and employed in a formal synthesis of Polyoxin... 

Regioselective addition of 2-methoxyfuran and 2-trimethylsilyloxyfuran to chromium(O) alkynylcarbene complexes furnished interesting dienyne and dienediyne carboxylates <07AGE2610>. The reaction likely proceeded through a formal vinylogous Michael addition adduct, as illustrated in the following example. 

Structural characterizations of reaction intermediates and products of the addition of 2-trimethylsilyloxyfuran to naphthoquinones <1998TA1257> and benzoquinones <1999TA4357> to form furanofuranones indicated that the reaction proceeded via Michael addition, rather than Diels-Alder cycloaddition, in which the type of intermediate 9 shown in Scheme 3 was observed by proton nuclear magnetic resonance (NMR) spectroscopy. 

A ry -selective, organocatalytic, enantioselective vinylogous Mukaiyama-Michael addition of 2-trimethylsilyloxyfuran to a,/ -unsaturated aldehydes to produce 7-butenolides was achieved by using a chiral amine catalyst... 

Vinylogous Mukaiyama-Michael additions of 2-trimethylsilyloxyfuran to 3-alkenoyl-2-oxazolidinones to provide 7-butenolides were shown to be /7-selective. The reaction could be rendered enantioselective in the presence of a (T symmetric copper-bisoxazoline complex <1997T17015, 1997SL568> or a l,T-binaphthyl-2,2 -diamine-nickel(ii) complex as catalyst, as depicted in Equation (16) <2004CC1414>. 

As shown in Equation (17), 2-trimethylsilyloxyfuran also participated in a triphenylphosphine-catalyzed substitution reaction with Morita-Baylis-Hillman acetates to provide interesting 7-butenolides regio- and diastereoselec-tively <2004AGE6689>. However, the reaction mechanism (vinylogous Michael vs. Diels-Alder) has not been distinguished. 

Trimethylsilyloxyfuran reacted stereoselectively with chiral tungsten carbene complexes in a Mukaiyama-Michael addition fashion to provide -products, as shown in Equation (18) <2005AGE6583>. The metal carbene in the butenolide product serves as a useful functional group for further transformations. 

Related Reagents. a,(3-Butenolide 7-Butyrolactone R)-Pantolactone p-Propiolactone 2-Trimethylsilyloxyfuran p-Vinyl-a,p-buten olide. 

The newest techniques employ silylation. Even the anions of saturated butenolides afford the enol ester on reaction with chlorotrimethylsilane91 applied to a butenolide the method readily supplies a 2-silyloxyfuran. Such ethers are even more easily procured by allowing a butenolide to react with chlorotrimethylsilane in the presence of triethylamine and zinc chloride but for reasons that remain unclear, acetonitrile is the only satisfactory solvent.92 A typical transformation of 2-trimethylsilyloxyfuran is shown in Scheme 19. 

The less well-studied 3-silyloxyfuran was shown to react with aldehydes in an aldol addition manner under Lewis acidic conditions. High 5yn-diastereoselectivity was obtained with bulky aldehydes <05OL387>. 4-Alkoxy-3-lithio-2-silyloxyfurans reacted with a variety of electrophiles to form 3-substituted tetronates after acidic hydrolysis <05SL2735>. Furans and 2-trimethylsilyloxyfuran are effective nucleophiles in the organocatalytic tandem... 

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