Synthesis of N-pentofuranosyl oxazolines and amides though the selective transformations of D-sugar acetonides

The method for synthesis of N-pentofuranosyl oxazolines was developed from the protected 1,2-O-acetonides of D-xylofuranose, -ribofuranose, and -arabinofuranose using boron trifluoride diethyl etherate, acetonitrile, and potassium hydrogen difluoride. A possible mechanism of the catalyzed reaction of acylated acetonides with acetonitrile in the presence of Lewis acid was considered in terms of the activation and cleavage of the 1,3-dioxalane part of the xylose derivative fol- lowed by the conversions of intermediates to α-isooxazoline. The hydrolysis reactions of N-α-glycosyl oxazolines were stud- ied in the acidic and neutral conditions. N-α-xylofuranosyl acetamide derivatives were prepared in high yields as a result of selective hydrolysis of protected α-xylofuranosyl isooxazolines in the neutral conditions.

Download Full-text

Enolic Ortho Esters. I. Preparation and Birch Reduction of Some Coumarinoid Ortho Esters

Australian Journal of Chemistry ◽

10.1071/ch9891235 ◽

1989 ◽

Vol 42 (8) ◽

pp. 1235 ◽

Cited By ~ 12

Author(s):

DJ Collins ◽

LM Downes ◽

AG Jhingran ◽

SB Rutschmann ◽

GJ Sharp

Keyword(s):

Carbon Tetrachloride ◽

Acid Hydrolysis ◽

Boron Trifluoride ◽

Boron Trifluoride Etherate ◽

High Yield ◽

Ortho Ester ◽

Birch Reduction ◽

High Yields ◽

Ortho Esters ◽

Hydrolysis Of

Phenolic ortho esters such as 4′,4′-dimethylspiro[2H-1-benzopyran-2,2′-[1,3]dioxolan] (7b) and 4′,4′-dimethyl-3,4-dihydrospiro[2H-1-benzopyran-2,2′-[1,3]dioxolan] (9c) were prepared in low yields by reaction of 2H-1-benzopyran-2-one (5) or 3,4-dihydro-2H-1-benzopyran-2-one (8a) with 2,2-dimethyloxiran in carbon tetrachloride in the presence of boron trifluoride etherate. 3,4-Dihydrospiro[2H-1-benzopyran-2,2′-[1,3] dioxoan ] (9a) and the corresponding 7-methoxy compound (9e) were obtained in high yield by reaction of (8a) or its 7-methoxy analogue (8b) with 1,2-bis(trimethylsily1oxy)ethane (10) in the presence of trimethylsilyl trifluoromethane-sulfonate . Birch reduction of phenolic ortho esters such as (9c) and (9e) afforded the enolic ortho esters 4′,4′-dimethyl-3,4,5,8-tetrahydrospiro[2H-1-benzopyran-2,2′-[1,3] dioxola n] (11a) and 7-methoxy-3,4,5,8-tetrahydrospiro[2H-1-benzopyran-2,2′-[1,3]dioxolan] (llc) in high yields. Birch reduction of 4′,4′,5′,5′-tetramethylspiro[2H-1-benzopyran-2,2′-[1,3]dioxolan] (7c) gave a 1 : 3 mixture of 4′,4′,5′,5′-tetramethyl-3,4-dihydrospiro[2H-1-benzopyran-2,2′-[l,3] dioxolan ] (9d) and the corresponding 3,4,5,8-tetrahydro compound (11b). Acid hydrolysis of the enolic ortho ester (11a) gave 67% of 2-hydroxy-2-methylpropyl 3-(2-oxocyclohex-3-enyl) propanoate (20).

Download Full-text

C-Glycosylation of Oxygenated Naphthols with 3-Dimethylamino-2,3,6-trideoxy-L-arabino-hexopyranose and 3-Azido-2,3,6-trideoxy-D-arabino-hexopyranose

Australian Journal of Chemistry ◽

10.1071/ch02236 ◽

2003 ◽

Vol 56 (8) ◽

pp. 787 ◽

Cited By ~ 14

Author(s):

Margaret A. Brimble ◽

Roger M. Davey ◽

Malcolm D. McLeod ◽

Maureen Murphy

Keyword(s):

Lewis Acid ◽

Boron Trifluoride ◽

Electronic Effects ◽

Effective Coupling ◽

Boron Trifluoride Diethyl Etherate ◽

Glycosyl Donor ◽

Aryl Glycosides ◽

Coupling Partner ◽

Fine Tune ◽

Glycosyl Donors

In connection with studies directed towards the synthesis of the pyranonaphthoquinone antibiotic medermycin, C-aryl glycosides were prepared by C-glycosylation of naphthols with glycosyl donors. Boron trifluoride diethyl etherate proved to be a suitable Lewis acid to promote the C-glycosylation, and use of the azido glycosyl donor proved more successful than using the dimethylamino glycosyl donor. 5-Hydroxy-1,4-dimethoxynaphthalene underwent facile C-glycosylation with two particular glycosyl donors, whereas 3-bromo-5-hydroxy-1,4-dimethoxynaphthalene was not an effective coupling partner with the same glycosyl donors. These studies indicate that subtle steric and electronic effects need to be considered in order to fine-tune C-glycosylations when using highly functionalized glycosyl donors.

Download Full-text

The reactions of some 5,6-Dihalogenocyclohex-2-ene-1,4-diones (1,4-Benzoquinone dihalides) in boron trifluoride diethyl etherate

Australian Journal of Chemistry ◽

10.1071/ch9730333 ◽

1973 ◽

Vol 26 (2) ◽

pp. 333 ◽

Cited By ~ 14

Author(s):

RK Norris ◽

S Sternhell

Keyword(s):

Boron Trifluoride ◽

Boron Trifluoride Etherate ◽

Hydrogen Halides ◽

Boron Trifluoride Diethyl Etherate ◽

High Yields ◽

Very High

Treatment of five 1,4-benzoquinone dihalides in boron trifluoride etherate gives very high yields of isomeric dihalogenohydroquinones. With the exception of the conversion of 5,6-dichlorocyclohex-2-ene-1,4- dione into 2,3-dichlorohydroquinone, which is a true keto-enol isomerization, these products arise through elimination of hydrogen halides followed by re-addition.

Download Full-text

Alkylation of Partially Protected Xylofuranoses and Tetritols with (2,2,3,3,4,4,5,5,6,6,7,7,7-Tridecafluoroheptyl)oxirane and the Stability of Protecting Acetal Groups Towards Lewis Acid-Type Catalyst

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc20011665 ◽

2001 ◽

Vol 66 (11) ◽

pp. 1665-1681 ◽

Cited By ~ 5

Author(s):

Karel Kefurt ◽

Jitka Moravcová ◽

Šárka Bambasová ◽

Kateřina Buchalová ◽

Barbora Vymětalíková ◽

...

Keyword(s):

Lewis Acid ◽

Boron Trifluoride ◽

Catalytic Amount ◽

Boron Trifluoride Diethyl Etherate ◽

Acid Type ◽

The Stability

1,2-O-Isopropylidene-3-O-methyl-α-D-xylofuranose (2), 1,2-O-isopropylidene-α-D-xylofuranose (3), 2,4-O-ethylidene-D-erythritol (4) and 1,3-O-ethylidene-D-threitol (5) were alkylated with racemic (2,2,3,3,4,4,5,5,6,6,7,7,7-tridecafluoroheptyl)oxirane (1) using boron trifluoride diethyl etherate as a catalyst. The desired mono- or disubstituted polyfluoroalkyl derivatives 6-11 were isolated only in low to medium yields. The fluoroalkylation was accompanied with disproportional distributions of the protecting acetal/ketal groups and polymerization of saccharides. Therefore the stability of 3, 4, 5, 5-O-acetyl-1,2-O-isopropylidene-α-D-xylofuranose (14) and 1,2-O-isopropylidene-α-D-glucofuranose (15) in the presence of a catalytic amount of boron trifluoride diethyl etherate was investigated in various solvents. A mechanism explaining the effect of the catalyst has been proposed.

Download Full-text

From dipivaloylketene to tetraoxaadamantanes

Beilstein Journal of Organic Chemistry ◽

10.3762/bjoc.14.1 ◽

2018 ◽

Vol 14 ◽

pp. 1-10 ◽

Cited By ~ 2

Author(s):

Gert Kollenz ◽

Curt Wentrup

Keyword(s):

Carboxylic Acid ◽

Reaction Mechanisms ◽

Membered Ring ◽

Flash Vacuum Pyrolysis ◽

Vacuum Pyrolysis ◽

Axially Chiral ◽

Acidic Conditions ◽

High Yields ◽

Neutral Conditions ◽

Hydrolysis Of

Dipivaloylketene (2) is obtained by flash vacuum pyrolysis of furan-2,3-dione 6 and dimerizes to 1,3-dioxin-4-one 3, which is a stable but reactive ketene. The transannular addition and rearrangement of enols formed by the addition of nucleophiles to the ketene function in 3 generates axially chiral 2,6,9-trioxabicyclo[3.3.1]nonadienes (bisdioxines) 4. When arylamines are used as the nucleophiles under neutral conditions, decarboxylation occurs during the formation of bisdioxines 8. However, when water or alcohols are added to 3 under acidic conditions, bisdioxine-carboxylic acids and esters 10 and 11 are obtained. Acid hydrolysis of the bisdioxines proceeds through the addition of water to a C=C double bond and results in a second transannular oxa-Michael-type reaction and generation of tetraoxaadamantanes 5. This reaction is decarboxylative when free carboxylic acid functions are present in the bisdioxines, thus forming 21 and 22, but carboxylic acid derivatives are preserved to yield compounds 20, 23, 25, 28, and 29. A hydrogenolysis of the dibenzyl ester 23 yields the free dicarboxylic acid 24. The tetraoxaadamantanes are formed in high yields (65–95%) in most cases, but the addition of water to the concave inside of the bisdioxines becomes severely hindered in cyclic derivatives, so that the 38-membered ring compound 32 requires microwave heating at 170 °C to form tetraoxaadamantane 33, and the catenated compound 36 and calix[6]arene derivative 37 did not form tetraoxaadamantanes. The reaction mechanisms of bisdioxine and tetraoxaadamantane formation are discussed.

Download Full-text