Boron Trifluoride Etherate/Iodide Ion as a Mild, Convenient and Regioselective Ether Cleaving Reagent

Mandal, Amritlal; Soni, Neetu; RATNAM, K. R.

doi:10.1055/s-1985-31174

Cited by 44 publications

(5 citation statements)

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“…The final production of amino triol 2 by deprotection of the 4-nitrobenzoate and reduction of the lactam lactol required that the methyl acetal first be cleaved. Simple hydrolysis with 1 N HCl provided the desired product in very low yield, and iodotrimethylsilane 37 or boron trifluoride etherate/tetrabutyl ammonium iodide afforded no reaction at all. More promising results were obtained with the use of trifluoroacetic acid (TFA), which provided the desired product 51 in variable yield .…”

Section: Resultsmentioning

confidence: 99%

Tandem [4 + 2]/[3 + 2] Cycloadditions of Nitroalkenes. 9. Synthesis of (−)-Rosmarinecine

1996

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(−)-Rosmarinecine (2) is the necine base portion of the pyrrolizidine alkaloid (−)-rosmarinine. (−)-Rosmarinecine is a representative of the group of pyrrolizidines that show a cis relationship between adjacent stereocenters C(1), C(7), and C(7a), in addition to a highly oxygenated skeleton. (−)-Rosmarinecine (2) has been synthesized in eight steps and 14.8% overall yield, as an illustration of a general approach for the construction of pyrrolizidines having this stereochemical feature. The key step in the asymmetric synthesis is a Lewis acid-promoted, tandem inter-[4 + 2]/intra-[3 + 2] cycloaddition between a fumaroyloxy nitroalkene and a chiral vinyl ether.

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Section: Resultsmentioning

confidence: 99%

Tandem [4 + 2]/[3 + 2] Cycloadditions of Nitroalkenes. 9. Synthesis of (−)-Rosmarinecine

1996

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“…A variety of reagents are known to convert epoxides to halohydrins; the ring openings of unsymmetrically substituted epoxides with Li 2 (NiBr 4 ) [10], LiX-(Bmim)PF 6 [11], haloborane reagents [12], Br 2 /PPh 3 [13], SmI 2 [14], Ti(O-i-pr) 4 [15], chlorosilanes [16], Lewis acids [3,17,18] and BF 3 -Et 2 O [19] have been reported. In particular metal halides such as Li/Ti [2], Sn [20], P [13], Cu [21], and Ni [10] easily induce epoxide-opening, in which the use of a stronger Lewis acid and a metal ion in structure of catalyst often results in low yields of the halohydrins when other sensitive functional groups are present [22].…”

Section: Introductionmentioning

confidence: 99%

H2TPP Organocatalysis in Mild and Highly Regioselective Ring Opening of Epoxides to Halo Alcohols by Means of Halogen Elements

2012

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Abstract:We found that elemental iodine and bromine are converted to trihalide nucleophiles (triiodine and tribromide anion, respectively) in the presence of catalytic amounts of meso-tetraphenylporphyrins (H 2 TPP). Therefore a highly regioselective method for the synthesis of -haloalcohols through direct ring opening of epoxides with elemental iodine and bromine in the presence of H 2 TPPs as new catalysts is described. At room temperature a series of epoxide derivatives were converted into the corresponding halohydrins resulting from an attack of trihalide species anion atoms at the less substituted carbon atom. This method occurs under neutral and mild conditions with high yields in various aprotic solvents, even when sensitive functional groups are present.

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“…[7] Boron halides are excellent reagents for the cleavage of aliphatic and aromatic ethers. [8,9] Several structurally modified B-haloorganoboranes have shown to cleave epoxides to halohydrins. [10,11] Also, α-pinene-based B-haloorganoboranes, d Ipc 2 BX (X = Cl, Br, I), as well as structurally modified Ter 2 BX have been used in the asymmetric cleavage of meso-epoxides to chiral halohydrins.…”

Section: Introductionmentioning

confidence: 99%

Monobromoborane - Dimethyl Sulfide—a Highly Promising Reagent for the Regio- and Chemoselective Brominative Cleavage of Terminal Epoxides into Vicinal Bromohydrins

Roy

Brown

2007

Aust. J. Chem.

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Monobromoborane-dimethyl sulfide (BH 2 Br-SMe 2 ) is a highly regio-and chemoselective reagent useful for the brominative cleavage of the epoxy moiety into bromohydrins in the presence of alkenes, alkynes, ethers, acetals, ketals, and acetonides at 0 • C, besides being an excellent hydroborating reagent. Several reactive functional groups, such as chloride, ketones, esters, nitriles, nitros, and thioethers, have been accommodated during such transformations. Although the reduction of acetophenone was completely suppressed at −25 • C, 4-chlorobenzaldehyde still underwent 12-13% reduction of an aldehydic group.

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Boron Trifluoride Etherate/Iodide Ion as a Mild, Convenient and Regioselective Ether Cleaving Reagent

Cited by 44 publications

References 0 publications

Tandem [4 + 2]/[3 + 2] Cycloadditions of Nitroalkenes. 9. Synthesis of (−)-Rosmarinecine

Tandem [4 + 2]/[3 + 2] Cycloadditions of Nitroalkenes. 9. Synthesis of (−)-Rosmarinecine

H2TPP Organocatalysis in Mild and Highly Regioselective Ring Opening of Epoxides to Halo Alcohols by Means of Halogen Elements

Monobromoborane - Dimethyl Sulfide—a Highly Promising Reagent for the Regio- and Chemoselective Brominative Cleavage of Terminal Epoxides into Vicinal Bromohydrins

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