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

1989 ◽  
Vol 42 (8) ◽  
pp. 1235 ◽  
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).

Enolic Ortho Esters. IV. Synthesis of the 8-α and 8-β Epimers of a 6-Oxa Steroidal Enolic Ortho Ester

1989 ◽  
Vol 42 (10) ◽  
pp. 1769 ◽  
Author(s):  
DJ Collins ◽  
AG Jhingran ◽  
SB Rutschmann
Keyword(s):  
Ethylene Oxide ◽  
Ethylene Glycol ◽  
Boron Trifluoride ◽  
Methanesulfonic Acid ◽  
Boron Trifluoride Etherate ◽  
Ortho Ester ◽  
Birch Reduction ◽  
Ortho Esters

Reaction of resorcinol (9) with methyl 1β-hydroxy-7aβ-methyl-5-oxo-2,3,3 a α,4,5,6,7,7a- octahydro-1H-indene-4α-carboxylate (10a) or with the corresponding 1,5-dioxo ester (15) in methanesulfonic acid gave ( �)-3,17 β-dihydroxy-6-oxaestra-l,3,5(10),8(9)-tetraen-7-one (11a) (98%), or (c)-3-hydroxy-6-oxaestra-1,3,5(10),8(9)-tetraene-7,17-dione (14) (91%), respectively. 3-O-Methylation of the phenolic keto lactone (14) followed by reaction with ethylene glycol gave (�)-17,17-ethylenedioxy-3-methoxy-6-oxaestra-1,3,5(10),8(9)- tetrae n-7-one (16). Reduction of this with lithium/ammonia afforded 77% of (�) 17,17-ethylenedioxy-3-methoxy-6-oxa-8 α-estra-1,3,5(10)-trien-7-one (71, which upon base-catalysed epimerization yielded 84% of the 8 β-epimer (19). Reaction of the 8 α-H lactone (17) or its 8 β- epimer (19) with ethylene oxide in the presence of boron trifluoride etherate yielded the corresponding phenolic ortho esters (�)-7,7:17,17-bis( ethylenedioxy )-3-methoxy-6-oxa-8 α-estra-1,3,S(10)- triene (23), and its 8 β- epimer (25), in 36 and 42% yields, respectively. Birch reduction of (23) and (25) afforded the corresponding enolic ortho ester ( �)-7,7:17,17-bis( ethylenedioxy )-3-methoxy-6-oxa-8 α-estra-2,5(10)- diene (26), and its 8 β-epimer (6), in 82 and 64% yields, respectively. Some related chemistry is described. The enolic ortho esters (26) and (6) were relatively inert to attack by methylmagne sium iodide under normal conditions.

On the synthesis of 3,4-dihydroxyprolines. II. Synthesis, stereochemistry and reactivity of some 3,4-Epoxy-DL-proline derivatives

1975 ◽  
Vol 28 (11) ◽  
pp. 2479 ◽  
Author(s):  
CB Hudson ◽  
AV Robertson ◽  
WRJ Simpson
Keyword(s):  
Acid Hydrolysis ◽  
Methyl Esters ◽  
High Yield ◽  
Butyl Esters ◽  
Epoxy Acids ◽  
Trifluoroperacetic Acid ◽  
Catalytic Hydrogenolysis ◽  
Direct Separation ◽  
Proline Derivatives ◽  
Hydrolysis Of

N-Protected esters of 3,4-dehydro-DL-proline react with trifluoroperacetic acid to give, in high yield, approximately equal amounts of the corresponding stereoisomeric 3,4-epoxy-DL-proline derivatives, direct separation of which proved difficult. However individual members of the two families were obtained by discovery of selective transformations and fractionations. Relative configurations of the two 3,4-epoxy-N-tosylproline methyl esters were established by borohydride reduction to authentic 4-hydroxy-N-tosylprolinols. Epoxide reduction is regioselective. Extensive p.m.r. analyses then permitted stereochemical assignment of other derivatives. These epoxides are remarkably resistant to catalytic hydrogenolysis, and to hydration in acid or alkali. N-Substituted 3,4-epoxyproline methyl esters undergo ready β-elimination in alkali to yield the corresponding 4-hydroxy-2,3- dehydroproline esters and ultimately the N-substituted pyrrole-2- carboxylic acid or ester. Prolonged aqueous acid hydrolysis of 3,4- epoxy-N-tosylprolines, or of their methyl esters, gives mixtures of 3,4-dihydroxy-N-tosyl-DL-prolines in the 2,3-cis-3,4-trans and 2,3- trans-3,4-trans families. Their stereochemistry was allotted from p.m.r. of the diacetate methyl esters. During acid hydrolysis of 3,4- epoxy-N-tosylproline methyl esters, the ester of the trans stereoisomer hydrolyses selectively, and some epimerization of the cis stereoisomer occurs. Ester hydrolysis is much faster than epoxide hydration. Anhydrous acid cleavage of 3,4-epoxy-N-tosyl-DL-proline t-butyl esters to the epoxy acids is unusually slow.

Hydrolysis of trioxaadamantane ortho esters. I. Dialkoxycarbocation – ortho ester equilibrium and acidity function

1984 ◽  
Vol 62 (6) ◽  
pp. 1068-1073 ◽  
Author(s):  
Robert A. McClelland ◽  
Patrick W. K. Lam
Keyword(s):  
Acid Concentration ◽  
Intramolecular Interaction ◽  
Uv Spectroscopy ◽  
Equilibrium Constants ◽  
Hydrolysis Product ◽  
Acidity Function ◽  
Ortho Ester ◽  
Aromatic Substituent ◽  
Ortho Esters ◽  
Hydrolysis Of

3-Aryl-2,4,10-trioxaadamantane ortho esters (T) undergo a rapid equilibration with a ring-opened dioxan-2-ylium ion (DH+) prior to hydrolysis to product (a 1,3,5-cyclohexanetriol monobenzoate). The cation is stable in concentrated H2SO4 solutions where it has been characterized by nmr spectroscopy. It is observed using uv spectroscopy in dilute acids, and the ratio [DH+]/[T] at equilibrium has been measured as a function of acidity. Reversibility of the ring opening is established by the pattern of plots of cation absorbance versus acid concentration and by the observation that solutions containing cation on neutralization or dilution yield ortho ester, not hydrolysis product. Equilibrium constants for the reaction [Formula: see text] have been measured by obtaining the acidity function HT for this system. The effects of the aromatic substituent and the steepness of the acidity function plot versus acid concentration are interpreted in terms of a strong intramolecular interaction in the cation between the cationic center and the hydroxyl oxygen.

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

2021 ◽  
Vol 65 (5) ◽  
pp. 558-567
Author(s):  
G. G. Sivets ◽  
A. V. Sivets
Keyword(s):  
Lewis Acid ◽  
Boron Trifluoride ◽  
Selective Hydrolysis ◽  
Boron Trifluoride Diethyl Etherate ◽  
Potassium Hydrogen ◽  
High Yields ◽  
Neutral Conditions ◽  
Hydrolysis Of ◽  
Hydrolysis Reactions

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.

Neuroleptic 2-chloro-11-(2-piperazineethoxy)-10,11-dihydrodibenzo[b,f]thiepins: Synthesis and pharmacology

1984 ◽  
Vol 49 (8) ◽  
pp. 1810-1815 ◽  
Author(s):  
Václav Bártl ◽  
Jiří Jílek ◽  
Jiřina Metyšová ◽  
Martin Valchář ◽  
Antonín Dlabač ◽  
...  
Keyword(s):  
Alkaline Hydrolysis ◽  
Boron Trifluoride ◽  
Boron Trifluoride Etherate ◽  
Dopamine Metabolism ◽  
Substitution Reactions ◽  
Activity Profile ◽  
Hydrolysis Of ◽  
Brain Striatum ◽  
Hydroxyethyl Piperazine ◽  
Central Depressant

A reaction of 8-chloro-10,11-dihydrodibenzo[b,f]thiepin-10-ol with 2-bromoethanol and boron trifluoride etherate produced the 2-bromoethyl ether II which was subjected to substitution reactions with 1-methylpiperazine, 1-(2-hydroxyethyl)piperazine, 1-(3-hydroxypropyl)piperazine and 1-ethoxycarbonylpiperazine to give the title piperazinoethoxy compounds IV-VII. Alkaline hydrolysis of the carbamate VII afforded the monosubstituted piperazine VIII. Compounds IV-VI are neuroleptics with an interesting activity profile: they are little toxic, have strong central depressant and antimorphine activity, mild cataleptic effects, they intensively increase the dopamine metabolism in the rat brain striatum and are almost free of the peripheral adrenolytic efficacy.

Enamines of 2,2-bis(ethylthio)ethanal: a convenient route to γ-keto crotonate derivatives

1983 ◽  
Vol 61 (11) ◽  
pp. 2466-2475 ◽  
Author(s):  
Gordon S. Bates ◽  
S. Ramaswamy
Keyword(s):  
Potassium Salt ◽  
Alkylating Agents ◽  
High Yield ◽  
Convenient Route ◽  
High Yields ◽  
Hydrolysis Of ◽  
Potential Precursor ◽  
Chiral Potential

A new α-oxoaldehyde reagent, 2,2-bis(ethylthio)ethanal 1, has been prepared in high yield from ethanedial. Alkylation of the potassium salt of the enamines of 1 with various alkylating agents followed by insitu hydrolysis of the intermediate imine afforded high yields of the alkylation products of 1. This new reagent was used in the synthesis of a chiral potential precursor of the macrocyclic fragment of cytochalasins A, B, and F, as well as in the syntheses of the physiologically active diolides pyrenophorin and norpyrenophorin.

Synthesis and structure of a stegane from dimethylmatairesinol

1984 ◽  
Vol 37 (8) ◽  
pp. 1775 ◽  
Author(s):  
RC Cambie ◽  
GR Clark ◽  
PA Craw ◽  
PS Rutledge ◽  
PD Woodgate
Keyword(s):  
Trifluoroacetic Acid ◽  
Oxidative Coupling ◽  
Boron Trifluoride ◽  
Boron Trifluoride Etherate ◽  
High Yield ◽  
X Ray Diffraction ◽  
X Ray

Oxidative coupling of dimethylmatairesinol with thallium tristrifluoroacetate (prepared in situ from thallium(III) oxide and trifluoroacetic acid) and boron trifluoride etherate gives a high yield of an isostegane which has been isomerized thermally to a stegane. Stereochemical assignments have been confirmed by X-ray diffraction studies.

Enolic Ortho Esters. III. Preparation of a Keto Acetal by Hydride Reduction of an Enolic Ortho Ester

1989 ◽  
Vol 42 (9) ◽  
pp. 1617 ◽  
Author(s):  
DJ Collins ◽  
LM Downes ◽  
M Kyriakou
Keyword(s):  
Lithium Aluminium Hydride ◽  
Ortho Ester ◽  
Hydride Reduction ◽  
Lithium Aluminium ◽  
High Yields ◽  
Ortho Esters

Lithium aluminium hydride reduction of the enolic ortho ester 4′,4′-dimethyl-3,4,5,8-tetra-hydrospiro [2H-l-benzopyran-2,21-[1,3]dioxolan] (8) in the absence of solvent gave 6-[21-(4″,4″- dimethyl-1″,3″-dioxolan-2″-yl)ethyl]cyclohex-3-en-1-one (11) which was isomerized to the α'β-unsaturated keto acetal (10). Similarly, hydride reduction of the phenolic ortho ester 4′-methyl-3,4-dihydrospiro[2H-1-benzopyran-2,2′-[1,3]dioxolan] (12a) and the 4′,4′-dimethyl analogue (12b), afforded the corresponding phenolic acetals (14a) and (14b) respectively, in high yields.′

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

1973 ◽  
Vol 26 (2) ◽  
pp. 333 ◽  
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.

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