Methyleneketenes and methylenecarbenes. XVI. The formation of Diphenylfuran-2-ones and 3-Phenylphthalide as minor products of the pyrolysis of diphenylmethyl propiolate

1981 ◽  
Vol 34 (7) ◽  
pp. 1467 ◽  
Author(s):  
RFC Brown ◽  
FW Eastwood ◽  
N Chaichit ◽  
BM Gatehouse ◽  
JM Pfeiffer ◽  
...  
Keyword(s):  
Structure Determination ◽  
Phenyl Ring ◽  
Diels Alder ◽  
Insertion Reaction ◽  
X Ray ◽  
Flash Vacuum Pyrolysis ◽  
Methyl Propiolate ◽  
Vacuum Pyrolysis ◽  
Labelling Experiment ◽  
A Minor

The formation of a mixture of lactones as a minor product of the flash vacuum pyrolysis of diphenyl-methyl propiolate (1) has been investigated further. ��� The diphenylfuran-2-ones (3), (4), and (5) are shown to be formed through an intramolecular insertion reaction of the methylenecarbene (2), formed from (1) at 640°, which leads to 5,5-diphenyl-furan-2(5H)- one (3) as the primary product. ��� 3-Phenylphthalide (8) is apparently formed by intramolecular Diels-Alder addition of the C≡C bond of (1) to one phenyl ring which acts as the diene component, followed by loss of acetylene from an intermediate barrelene derivative (10). This is confirmed by a deuterium labelling experiment. ��� 1-Phenyl-2-benzoxepin-3(1H)-one (7), considered at first as a possible intermediate in the pyrolysis of (1), is synthesized in six steps from 2-aminobenzophenone, and its X-ray structure determination is reported. On pyrolysis at 640°/0.07 mm (7) decarbonylates smoothly to give 2-vinylbenzophenone.

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).

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.

The Reaction of 2-Hydro-2-oxo-5,6-benzo-l,3,2λ4-dioxaphosphorin-4-one with Imines and Carbonyl Compounds; Unusual Formation and First X-Ray Crystal Structure Determination of a Benzodioxaphosphepinone Ring System

1996 ◽  
Vol 51 (10) ◽  
pp. 1501-1510 ◽  
Author(s):  
Thomas Kaukorat ◽  
Ion Neda ◽  
Holger Thönnessen ◽  
Peter G. Jones ◽  
Reinhard Schmutzler
Keyword(s):  
Crystal Structure ◽  
Oxygen Atom ◽  
Structure Determination ◽  
Ring Expansion ◽  
Ring System ◽  
Crystal Structure Determination ◽  
Insertion Reaction ◽  
X Ray ◽  
Ir Spectroscopic

On treatment of 2-hydro-2-oxo-5,6-benzo-1,3,2λ4-dioxaphosphorin-4-one (1) with the inline trimers trim ethyl- and tribenzyltriazine and the (monomeric) methylene-tert-butylimine, an insertion reaction of the imine molecule into the P-H bond of 1 took place, forming com pounds 2 -4 . Similar results were obtained when 1 was allowed to react with aldimines, asymmetric at carbon, leading to 5-7 . The diastereotopic properties of 5 - 7 were observed by 1H NMR spectroscopy. NMR and IR spectroscopic investigations on 5 - 7 indicated > C = O···H-N < interactions. Upon reaction of 1 with hexafluoroacetone, trifluoroacetophenone or phenyltrifluoromethylketimine, the derivatives 8 -1 0 , involving a P-O-C fragment, were obtained. The formation of the isomeric “alcohol form ”, bearing a P-C-OH fragment, could not be proved. In the reaction of 1 with various o-quinones. one of the oxygen atom s of the quinone was found to be bonded to phosphorus, whereas the hydrogen atom was found to migrate to the second oxygen atom . Upon reaction of 1 with chloral, an unusual ring expansion took place with formation of the benzodioxaphosphepinone (14). The reaction of 1 with other aldehydes could not be realized. In the reaction of 14 with triethylamine, the ammonium salt 15 was formed. For the first time, an X-ray crystal structure determination of a dioxaphosphepinone ring system was conducted; in 15 the seven-membered ring displays a pseudo tub conformation.

New Thermal and Photochemical Routes to Dewar Furan and Other Isomers on the C4H4O Energy Surface: the Role of Isobenzofuran as a Trapping Agent

1991 ◽  
Vol 44 (9) ◽  
pp. 1275 ◽  
Author(s):  
RN Warrener ◽  
IG Pitt ◽  
RA Russell
Keyword(s):  
High Temperatures ◽  
Low Temperatures ◽  
Energy Surface ◽  
Thermal Study ◽  
Diels Alder ◽  
Flash Vacuum Pyrolysis ◽  
Vacuum Pyrolysis ◽  
Benzene Oxide ◽  
Trapping Agent

Photolysis of the specially synthesized substrate (39) leads to quantitative fragmentation into the phthalimide (56) and Dewar furan (4a). Dewar furan has only transient existence even at -65°, yet can be trapped effectively with isobenzofuran but not furan. Rapid isomerization to cycloprop-2-enecarbaldehyde (57) occurs at the photolysis temperatures and this product is also trapped by the isobenzofuran . In the absence of trapping agent, photolysis of (39) produces some furan but no 1H n.m.r . evidence can be obtained for (4a) or (57), even at low temperatures (-85°). Separate irradiation of (57) causes extensive polymerization, without yielding other recognizable products. Furan is concluded, therefore, to arise from photoisomerization of (4a) rather than photochemical or thermal isomerization of (57). Separate thermal study of (57) shows that isomerization to furan only occurs above 420°. Flash vacuum pyrolysis of the polycyclic epoxide (72) provides a new retro- Diels-Alder route to (57) which likely proceeds via (4a) as an intermediate. At high temperatures (57) is isomerized to furan. A new Dewar benzene oxide (41) and Dewar benzene (45) are reported en route to the photosubstrates (39) and (50) respectively. Photolysis of (50) provides a high-yielding source of cyclobutadiene , which in the absence of trapping agent yields the syn-dimer (59).

Diels-Alder dimerization of a hexenylidene-substituted Benzofuran-2(3H)-one

1983 ◽  
Vol 36 (2) ◽  
pp. 389 ◽  
Author(s):  
H Becker ◽  
SR Hall ◽  
BW Skelton ◽  
AH White
Keyword(s):  
Double Bond ◽  
Single Crystal ◽  
Structure Determination ◽  
Diels Alder ◽  
Exocyclic Double Bond ◽  
X Ray ◽  
Aromatic Systems ◽  
Aromatic Hydrogen

(Z)-7-t-Butyl-5 methoxy-3-[(Z)-2?-methoxy-5,5'-dimethyl-4'-oxohex-2'-enylidene]benzofuran-2(3H)-one has been found to undergo Diels-Alder dimerization in which the exocyclic double bond adds to the s-cis diene moiety. The stereochemistry of the Diels-Alder dimer was established by a single-crystal X-ray structure determination. Crystals of the dimer, C44H56O10, are monoclinic, P21/n, a 12.23(1), b 19.43(2), c 18.71(2) �, β 107.76(7)�, Z 4; a residual of 0.046 was obtained for the 2519 'observed' reflections. In the dimer, two benzofuranone moieties are situated so as to be vicinal spiro substituents of the cyclohexene formed in the Diels-Alder addition. The bond between the two benzofuranone units is unusually long [1.597(6)�]. The shielding of one aromatic hydrogen in the n.m.r. spectrum of the dimer results from the disposition of the two aromatic systems.

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.

Crystal and Molecular Structure of 4-Arylhexahydro-1H,3H-pyrido[1,2-c]pyrimidine-1,3-dione Derivatives

2002 ◽  
Vol 57 (11) ◽  
pp. 1315-1319 ◽  
Author(s):  
Irena Wolska ◽  
Franciszek Herold
Keyword(s):  
Molecular Structure ◽  
Crystal Structure ◽  
Hydrogen Bonds ◽  
Structure Determination ◽  
Phenyl Ring ◽  
Crystal And Molecular Structure ◽  
X Ray ◽  
Saturated Ring ◽  
Centrosymmetric Dimers

The X-ray crystal structure determination of 4-(2-methylphenyl)hexahydro-1H,3H-pyrido[ 1,2-c]pyrimidine-1,3-dione (2) and 4-(3-methylphenyl)hexahydro-1H,3H-pyrido[1,2-c]- pyrimidine-1,3-dione (3) is reported. The crystal structures show the formation of centrosymmetric dimers via intermolecular N-H···O hydrogen bonds. The saturated ring adopts a slightly distorted halfchair conformation in both 2 and 3. In either compound the planar phenyl ring is twisted with respect to the pyrimidine-1,3-dione fragment.

Preparation of the First Isobenzofuran Containing Two Ring Nitrogens: A New Diels - Alder Diene for the Synthesis of Molecular Scaffolds Containing One or More End-Fused 3,6-Di(2-pyridyl)pyridazine Ligands

2003 ◽  
Vol 56 (8) ◽  
pp. 811 ◽  
Author(s):  
Ronald N. Warrener ◽  
Douglas N. Butler ◽  
Davor Margetic
Keyword(s):  
Diels Alder ◽  
Molecular Scaffolds ◽  
Flash Vacuum Pyrolysis ◽  
Vacuum Pyrolysis ◽  
Ring Nitrogen ◽  
Molecular Architectures ◽  
First Time

Preparation of a stable, crystalline isobenzofuran containing two ring-nitrogen atoms, 4,7-di(2-pyridyl)-5,6-diazaisobenzofuran (diaza-IBF) (12), is reported here for the first time. Diaza-IBF was prepared using the s-tetrazine-induced fragmentation of 1,4-di(2-pyridyl)-5,8-epoxy-5,8-dihydrophthalazine (9), for which a synthesis is provided. Diaza-IBF was also prepared by flash vacuum pyrolysis (FVP) of the isomeric N-methyl-1,4-di(2-pyridyl)-5,8-epoxy-5,6,7,8-tetrahydrophthalazine-6,7-dicarboximides (18) and (19), formed in three steps from furan, N-methyl maleimide, and 3,6-di(2-pyridyl)-s-tetrazine. Diaza-IBF was employed in cycloaddition protocols with alkenes to form scaffold mono- or bis-3,6-di-(2-pyridyl)-pyridazine ligands having novel molecular architectures.

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