Synthesis of 1,8,8-Trimethyl-6,10-dioxaspiro[4.5]dec-2-ene-1-ethanol; X-Ray Crystallography of (1RS,2SR)-1,8,8-Trimethyl-1-(prop-2'-enyl)-6,10-dioxaspiro[4.5]dec-2-yl Benzoate

1994 ◽  
Vol 47 (4) ◽  
pp. 739 ◽  
Author(s):  
DJ Collins ◽  
GD Fallon ◽  
RP Mcgeary
Keyword(s):  
Oxidative Cleavage ◽  
Quantitative Yield ◽  
Borohydride Reduction ◽  
X Ray ◽  
X Ray Crystallography ◽  
Flash Vacuum Pyrolysis ◽  
Hydride Reduction ◽  
Tetrabutylammonium Fluoride ◽  
Vacuum Pyrolysis ◽  
Relative Stereochemistry

Reaction of 2-methyl-2-(prop-2′-enyl)cyclopentane-1,3-dione (2) with 2,2-dimethylpropane-1,3-diol gave 1,8,8-trimethyl-1-(prop-2′-enyl)-6,10-dioxaspiro[4.5]decan-2-one (3), hydride reduction of which afforded a 1:1 epimeric mixture of the corresponding alcohols (4a) and (4b). They were separated, and the derived benzoates (5a) and (5b) were each subjected to a three-step sequence of oxidative cleavage, borohydride reduction and silylation to give the pure epimers (8a) and (8b) of 1,8,8-trimethyl-1-(2′-t-butyldimethylsilyloxyethyl)-6,10-dioxaspiro[4.5]dec-2-yl benzoate. Flash vacuum pyrolysis of a mixture of these epimeric benzoates (8a,b) gave an almost quantitative yield of 1,8,8-trimethyl-1-(2′-t-butyldimethylsilyloxyethyl)-6,10-dioxaspiro[4.5]dec-2-ene (9a), treatment of which with tetrabutylammonium fluoride afforded the corresponding alcohol (9b). The relative stereochemistry of (1RS,2SR)-1,8,8-trimethyl-1-(prop-2′-enyl)-6,10-dioxaspiro [4.5]dec-2-yl benzoate (5b) was established by X-ray crystallography.

The Pyrolytic Rearrangement of 1-Alkynoyl-3-methylpyrazoles: Synthesis of Pyrazolo[1,5-a]pyridin-5-ols and Related Compounds

1994 ◽  
Vol 47 (6) ◽  
pp. 991 ◽  
Author(s):  
RFC Brown ◽  
FW Eastwood ◽  
GD Fallon ◽  
SC Lee ◽  
RP Mcgeary
Keyword(s):  
Carbon Chain ◽  
Ring Structure ◽  
High Yield ◽  
Methyl Group ◽  
X Ray ◽  
X Ray Crystallography ◽  
Flash Vacuum Pyrolysis ◽  
Vacuum Pyrolysis ◽  
Fused Ring ◽  
Related Compounds

Flash vacuum pyrolysis of 1-(alkyn-2′-oyl)-3-methylpyrazoles at 650°/0.03 mm forms pyrazolo[1,5-a]pyridin-5-ols, often in high yield, which may bear substituents at C2, C3 or C7. In the absence of a 3-methyl group in the precursor, N-ethynylpyrazoles are formed in low yield. The formation of both types of product is interpreted as involving 3-(N-pyrazolyl)propadienones formed by N1 → N2 migration of the N-alkynoyl group with inversion of the three-carbon chain. The fused-ring structure of 2-methylpyrazolo[1,5-a]pyridin-5-ol (25) was established by X-ray crystallography of the O-benzoyl derivative (27).

Catalyst-Free Synthesis of Diastereomerically Pure 3-Sulfonyl­azetidin-2-ones via Microwave-Assisted Tandem Wolff Rearrangement–Staudinger Cycloaddition

Synthesis ◽  
2020 ◽  
Author(s):  
Mikhail Krasavin ◽  
Judith Synofzik ◽  
Olga Bakulina ◽  
Olga Balabas ◽  
Dmitry Dar’in
Keyword(s):  
Drug Design ◽  
Single Crystal ◽  
Wolff Rearrangement ◽  
X Ray ◽  
Design And Optimization ◽  
X Ray Crystallography ◽  
Microwave Assisted ◽  
Catalyst Free ◽  
Relative Stereochemistry ◽  
Wide Range

A wide range of α-diazo-β-ketosulfones have been applied to thermally promoted tandem Wolff rearrangement – Staudinger [2+2] cycloaddition with imines to give polysubstituted β-lactam sulfones. Dia­stereomerically pure syn-diastereomers were obtained in good yields and the relative stereochemistry was confirmed by single-crystal X-ray crystallography. These findings significantly expand the scope of this transformation, in contrast to substantial limitations reported previously. Moreover, this methodology enables flexible exploration of new substitution patterns around the privileged β-lactam core for drug design and optimization.

Studies Directed Towards the Total Synthesis of Anticapsin. X-Ray Crystal-Structure of (1RS,2SR,4RS,5RS,6SR)-5-Hydroxy-2-phthalimido-1-trimethylsilyloxy-bicyclo[2.2.2]octane-2,6-carbolactone

1990 ◽  
Vol 43 (11) ◽  
pp. 1827 ◽  
Author(s):  
MJ Crossley ◽  
TW Hambley ◽  
AW Stamford
Keyword(s):  
Crystal Structure ◽  
Amino Acid ◽  
Total Synthesis ◽  
Synthetic Approach ◽  
Hydrogen Atoms ◽  
Full Matrix ◽  
X Ray ◽  
X Ray Crystallography ◽  
Relative Stereochemistry ◽  
Atomic Parameters

The relative stereochemistry of methyl 2-phthalimido-1- trimethylsilyloxybicyclo[2.2.2]oct-5-ene-2-carboxylate (9) and its 5,6-epoxide (10), intermediates in a synthetic approach to the amino acid antibiotic anticapsin, were established by the TiCl4-mediated cyclization of (10) to the carbolactone (12); the structure of which was proved by single-crystal X-ray crystallography. Full-matrix least- squares refinement of all atomic parameters with individual isotropic thermal parameters for the hydrogen atoms by using 1446 reflections converged at R 0.036. Crystals of (12) are monoclinic, P21/c, a 12.342(3), b 12.239(2), c 13.405(3) Ǻ, β 99.34(2)°, Z 4.

Unexpected Pyrolytic Behaviour of Substituted Benzo[c]thiopyran and Thieno[2,3-c]thiopyran S,S-dioxides

2014 ◽  
Vol 67 (9) ◽  
pp. 1288 ◽  
Author(s):  
R. Alan Aitken ◽  
Clémence Hauduc ◽  
M. Selim Hossain ◽  
Emily McHale ◽  
Adrian L. Schwan ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Ring Expansion ◽  
Hydrogen Atom Transfer ◽  
Membered Ring ◽  
X Ray ◽  
Flash Vacuum Pyrolysis ◽  
Vacuum Pyrolysis ◽  
Higher Temperature ◽  
Intramolecular Hydrogen ◽  
Carbonyl Products

Flash vacuum pyrolysis (FVP) of benzo[c]thiopyran S,S-dioxide (1) results in formation of indene and 2-vinylbenzaldehyde as previously described. A range of eight analogues with various substitution patterns are found to behave differently. In general, there is no extrusion of SO2 to give products analogous to indene, but unsaturated carbonyl products analogous to 2-vinylbenzaldehyde are formed in most cases by way of ring expansion to a 7-membered ring sultine, extrusion of SO, and intramolecular hydrogen atom transfer. Other processes observed include formation of anthracene via an isomeric 7-membered sultine with loss of SO, CO and methane or butane, and formation of 4-ethylidene-4,5-dihydrocyclobuta[b]thiophenes by way of SO loss, a radical rearrangement, and extrusion of acetone. The analogues with a halogen substituent at position 8 on the benzene ring require a higher temperature to react and give naphthalene resulting from net elimination of HX and SO2. The X-ray crystal structure of 1 is also reported.

A Pyrolytic Approach to 2-Hydroxy-7-methoxy-5-methyl-1-naphthoic Acid

1995 ◽  
Vol 48 (5) ◽  
pp. 1055 ◽  
Author(s):  
RFC Brown ◽  
FW Eastwood ◽  
JM Horvath
Keyword(s):  
Carboxylic Acid ◽  
Condensation Product ◽  
Quantitative Yield ◽  
Meldrum's Acid ◽  
Meldrum’S Acid ◽  
Title 1 ◽  
Flash Vacuum Pyrolysis ◽  
Vacuum Pyrolysis ◽  
Naphthoic Acid

Condensation of 4-methoxy-2,6-dimethylbenzaldehyde with Meldrum's acid, and flash vacuum pyrolysis of the condensation product (12) gave in almost quantitative yield 7-methoxy-5-methyl-2-naphthol (9). This naphthol is a precursor of the title 1-carboxylic acid (6), an intercalating moiety of enediyne and other antibiotics.

Diastereoselective Propionitrile Oxide Cycloaddition Reactions With Some γ-Substituted α-Methylene-γ-butyrolactones

1993 ◽  
Vol 46 (9) ◽  
pp. 1401 ◽  
Author(s):  
SM Pereira ◽  
GP Savage ◽  
GW Simpson ◽  
RJ Greenwood ◽  
MF Mackay
Keyword(s):  
Dipolar Cycloaddition ◽  
Cycloaddition Reactions ◽  
X Ray ◽  
X Ray Crystallography ◽  
Relative Stereochemistry

A number of γ-substituted α-methylene-γ-butyrolactone derivatives underwent 1,3-dipolar cycloaddition with propionitrile oxide to give spiro Δ2-isoxazolines. The reaction proceeded regiospecifically and with high diastereoselectivity. The products of anti addition predominated. The regiochemistry of addition and relative stereochemistry of the products were determined by a combination of n.O.e ., HETCOR and DOUBTFUL n.m.r. experiments. The assignment was confirmed in one case by X-ray crystallography.

Unusual Weiss–Cook condensation of dimethyl 2,3-dioxobutanedioate and dimethyl 3-oxoglutarate

1994 ◽  
Vol 72 (4) ◽  
pp. 1162-1164 ◽  
Author(s):  
Ghislain Deslongchamps ◽  
Daniel Mink ◽  
Paul D. Boyle ◽  
Nina Singh
Keyword(s):  
Sodium Chloride ◽  
Dimethyl Sulfoxide ◽  
Reaction Pathway ◽  
Quantitative Yield ◽  
X Ray ◽  
X Ray Crystallography ◽  
Kinetically Controlled

The Weiss–Cook condensation of dimethyl 2,3-dioxobutanedioate with two equivalents of dimethyl 3-oxoglutarate in aqueous bicarbonate produces an "abnormal" product, pentamethyl cis-3-(carbomethoxymethyl)-3,7-dihydroxy-2-oxabicyclo-[3.3.0]oct-7-ene-1,4,5,6,8-pentacarboxylate 7, whose structure has been determined by X-ray crystallography. Rrapcho decarbomethoxylation (sodium chloride, aqueous dimethyl sulfoxide, 140 °C) of this compound produces dimethyl cis-3,7-dioxobi-cyclo[3.3.0]octane-1,5-dicarboxylate 4 in quantitative yield. These results suggest that compound 7 may be the product of a kinetically controlled reaction pathway involving 4-hydroxypent-2-en-1-one intermediate 5. Heating of 7 in dimethyl sulfoxide may have promoted thermodynamic equilibration to a Weiss–Cook product, which then decarbomethoxylated to produce 4.

Studies of Australian Soft Corals .XXXVII. The Structure Determination of 2 Cembranolide Diterpenes From Soft Corals of the Genus Efflatounaria (Coelenterata, Octocorallia, Alcyonacea)

1986 ◽  
Vol 39 (1) ◽  
pp. 123 ◽  
Author(s):  
BF Bowden ◽  
JC Coll ◽  
LM Engelhardt ◽  
GV Meehan ◽  
GG Pegg ◽  
...  
Keyword(s):  
Structure Determination ◽  
Soft Coral ◽  
Soft Corals ◽  
X Ray ◽  
X Ray Crystallography ◽  
Coral Genus ◽  
Relative Stereochemistry ◽  
Chemical Correlation ◽  
Absolute Stereochemistry

Two isomeric 7,8-epoxycembra-3,11,15-trien-16,2-olides have been isolated from different species of the soft coral genus Efflatounaria. The structure of each was deduced spectroscopically , and the relative stereochemistry of one was determined by X-ray crystallography. The absolute stereochemistry of each cembranolide was obtained by chemical correlation with known compounds.

scholarly journals Synthesis, structure, and first reactions of a new class of thiacyclophanes

2017 ◽  
Vol 95 (3) ◽  
pp. 278-285 ◽  
Author(s):  
Arunachalam Kannan ◽  
Henning Hopf ◽  
Ina Dix ◽  
Peter G. Jones ◽  
Ludger Ernst
Keyword(s):  
Spectroscopic Data ◽  
Phase Transfer Catalysis ◽  
Phase Transfer ◽  
X Ray ◽  
Flash Vacuum Pyrolysis ◽  
New Class ◽  
Product Mixture ◽  
Vacuum Pyrolysis ◽  
Molecular Bridge ◽  
Meta Isomer

In our effort to prepare [m.n]cyclophanes carrying functional groups in their molecular bridges, the thiacyclophanes 14, 19, 20, and 21 have been prepared by simple routes from the pseudo-gem dibromide 10a and the corresponding bis-thiol 10b. The triply-bridged bis-thia-cyclophanes 14, and 19-21 were characterized by their spectroscopic data as well as by X-ray structural analyses. The meta-isomer 20 was oxidized to the bis-sulfone 23, which on flash vacuum pyrolysis (FVP) yielded a product mixture presumably containing the hydrocarbon 26 with a cleaved molecular bridge. Subjecting 23 to Ramberg-Bäcklund conditions (CCl4, NaOH, phase transfer catalysis) provided the chloride 24 in poor yield (9%), a [2.2]paracyclophane in which the new molecular bridge is fully conjugated.

The Chemistry of 5-Oxodihydroisoxazoles. IX. Annelated Pyrimidines by Flash Vacuum Pyrolysis

1994 ◽  
Vol 47 (7) ◽  
pp. 1263 ◽  
Author(s):  
RH Prager ◽  
Y Singh
Keyword(s):  
Quantitative Yield ◽  
Flash Vacuum Pyrolysis ◽  
Vacuum Pyrolysis

3-( Heterocyclylamino ) acrylates and analogues undergo smooth cyclization in close to quantitative yield under conditions of flash vacuum pyrolysis at 530°. Heterocycles which give annelated pyrimidines by this procedure include quinoline (seven examples), isoquinoline, pyridine and pyrimidine.

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