Enolic Ortho Esters. VIII Synthesis of (2S,3S)-2,3-Bis(methoxymethyl)-1,4,6-trioxaspiro[4.5]dec-7-ene

1998 ◽  
Vol 51 (11) ◽  
pp. 1025 ◽  
Author(s):  
David J. Collins ◽  
Ian T. Crosby
Keyword(s):  
Lewis Acid ◽  
Ortho Ester ◽  
Keto Ester ◽  
Catalysed Reaction ◽  
Ketene Acetal ◽  
Ortho Esters

Enolic ortho ester (2S,3S)-2,3-bis(methoxymethyl)-1,4,6-trioxaspiro[4.5]dec-7-ene (10b) was synthesized in 65% yield by cycloadditon of acrolein with the ketene acetal (4S,5S)-4,5-bis(methoxymethyl)-2-methylidene-1,3-dioxolan (7), derived by potassium t-butoxide treatment of (4S,5S)-4,5-bis(methoxy- methyl)-1,3-dioxolan (4). Lewis acid catalysed reaction (TiCl4, CH2Cl2, –78°) of the enolic ortho ester (10b) with the ketene silyl acetal 3-phenylmethyl-2-trimethylsilyloxy-4,5-dihydrofuran (15) afforded the formyl keto ester 3-[4′,5′-bis(methoxymethyl)-2′-(4′′-oxobutyl)-1′,3′-dioxolan-2′-yl]-3-phenylmethyl-4,5-dihydrofuran-2(3H)-one (16) (39%) with only poor diastereoselectivity. Attempts to make the bis(phenylmethyl) analogue (10a) of enolic ortho ester (10b) were thwarted by the finding that the required ketene acetal (9), analogous to (7), could not be generated by elimination from (4S,5S)-2-bromomethyl-4,5-bis(phenylmethyl)-1,3-dioxolan (6), or from the derived phenyl selenoxide (8), under a variety of conditions.

scholarly journals Functionalization of N-tosyl-2-pyridinone with silyl ketene acetal catalyzed by Lewis acid, and synthetic studies of corynantheidol

ARKIVOC ◽  
2003 ◽  
Vol 2003 (8) ◽  
pp. 232-246 ◽  
Author(s):  
Kou Hiroya ◽  
Rumi Jouka ◽  
Osamu Katoh ◽  
Takashi Sakuma ◽  
Michiko Anzai ◽  
...  
Keyword(s):  
Lewis Acid ◽  
Ketene Acetal ◽  
Synthetic Studies

The Conversion of Steroidal Ring B Lactones into Ortho Esters: Preparation of 7,7-Dimethoxy-6-oxaestra-1,3,5(10)-triene Derivatives

1998 ◽  
Vol 51 (11) ◽  
pp. 1003 ◽  
Author(s):  
David G. Bourke ◽  
David J. Collins
Keyword(s):  
Acetic Acid ◽  
Phenolic Acid ◽  
Sodium Methoxide ◽  
Reaction Sequence ◽  
Ortho Ester ◽  
Methyl Trifluoromethanesulfonate ◽  
Ortho Esters

17β-t-Butyldimethylsilyloxy-3-methoxy-6-oxaestra-1,3,5(10)-trien-7-one (1), prepared in three steps from 17b-hydroxy-3-methoxy-6-oxaestra-1,3,5(10),8-tetraen-7-one (5a), was converted via the corresponding phenolic acid into 1β-t-butyldimethylsilyloxy-5β-(2′-t-butyldimethylsilyloxy-4′-methoxyphenyl)-N,7aβ-dimethyl-N-phenyl-2,3,3aα,4,5,6,7,7a-octahydro-1H-indene-4α-carboxamide (17c). Subjection of (17c) to a reaction sequence with methyl trifluoromethanesulfonate, sodium methoxide/methanol, and then dry methanol/acetic acid gave a low yield (12%) of the ortho ester 3,7,7,17β-tetramethoxy- 6-oxaestra-1,3,5(10)-triene (2b), together with 5β-(2′-hydroxy-4′-methoxyphenyl)-1β-methoxy-N,7aβ-dimethyl-N-phenyl-2,3,3aα,4,5,6,7,7a-octahydro-1H-indene-4α-carboxamide (17e) (29%), 8% of (17a), the 1β-hydroxy analogue of (17e) and 3% of methyl 5-(2′-hydroxy-4′-methoxyphenyl)-1β-methoxy-7aβ-methyl-2,3,3aα,4,5,6,7,7a-octahydro-1H-indene-4α-carboxylate (11c). The outcome of this reaction sequence was complex, and very sensitive to minor changes in conditions. Several related transformations are described, and possible mechanistic pathways are discussed.

scholarly journals Four New Sesquiterpenoids from Ligularia subspicata Collected in China; Isolation of a Bakkane-type Lactone, an Eremophilane-type Lactone, and Two Ortho Esters

2015 ◽  
Vol 10 (6) ◽  
pp. 1934578X1501000
Author(s):  
Yoshinori Saito ◽  
Takanori Otsubo ◽  
Yuko Iwamoto ◽  
Katsuyuki Nakashima ◽  
Yasuko Okamoto ◽  
...  
Keyword(s):  
Sichuan Province ◽  
Ortho Ester ◽  
Type Compound ◽  
Ortho Esters ◽  
First Time

A bakkane type lactone, an eremophilane type lactone, and two ortho esters were isolated from Ligularia subspicata collected in Sichuan Province, China. The ortho ester type compound has been isolated from Ligularia for the first time.

Lewis acid-catalysed reaction of (cyclo)alkenes with oxiranes

2000 ◽  
Vol 41 (9) ◽  
pp. 1483-1486 ◽  
Author(s):  
David Munro ◽  
Chris Newman
Keyword(s):  
Lewis Acid ◽  
Catalysed Reaction

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.

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).

Asymmetric Synthesis ofβ-Amino-α-Hydroxy Acids through Lewis Acid-Mediated Addition of Ketene Acetal to Imines

2001 ◽  
Vol 74 (9) ◽  
pp. 1667-1672 ◽  
Author(s):  
Hyun-Joon Ha ◽  
Young-Gil Ahn ◽  
Jun-Sik Woo ◽  
Gwan Sun Lee ◽  
Won Koo Lee
Keyword(s):  
Asymmetric Synthesis ◽  
Lewis Acid ◽  
Hydroxy Acids ◽  
Ketene Acetal
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