Methyleneketenes and methylenecarbenes. III. Pyrolytic synthesis of arylacetylenes and their thermal rearrangements involving arylrnethylenecarbenes

1974 ◽  
Vol 27 (11) ◽  
pp. 2391 ◽  
Author(s):  
RFC Brown ◽  
FW Eastwood ◽  
KJ Harrington ◽  
GL McMullen
Keyword(s):  
Flash Vacuum Pyrolysis ◽  
Vacuum Pyrolysis ◽  
Thermal Rearrangements ◽  
Isopropylidene Malonate ◽  
Derivatives Of

Flash vacuum pyrolysis (550-600�) of 5-benzylidene derivatives of 2,2- dimethyl-1,3-dioxan-4,6-dione(isopropylidene malonate) gives phenylacetylenes bearing m- or p-substituents (H, Me, MeO, Cl, CN)in 64-98% yield. o-Methoxy- and o-phenyl-benzylidene derivatives give the arylacetylenes even at 420�. Arylacetylenes equilibrate with arylmethylenecarbenes, ArCH=C:, at 550-720�, as shown by labelling experiments using 13C and by the formation of products of interaction with o-substituents. Methylenebenzocyclobutene and o-tolylacetylene each form indene at 700-720�.

Methyleneketenes and methylenecarbenes. IV. Pyrolysis of 5-Heteroarylmethylene-2,2-dimethyl-l,3-dioxan-4,6-diones to give phenolic benzothiophens, benzofurans and indoles

1974 ◽  
Vol 27 (12) ◽  
pp. 2605 ◽  
Author(s):  
GJ Baxter ◽  
RFC Brown ◽  
GL McMullen
Keyword(s):  
Flash Vacuum Pyrolysis ◽  
Vacuum Pyrolysis ◽  
Synthetic Sequence ◽  
Heterocyclic Aldehydes ◽  
Derivatives Of

The synthetic sequence leading from o-tolualdehyde to 2-naphthol1 has been applied to seven five membered heterocyclic aldehydes bearing adjacent methyl substituents. Flash vacuum pyrolysis of the corresponding 5-heteroarylmethylene-2,2-dimethyl-1,3-dioxan-4,6-diones gave hydroxy derivatives of the benzologous systems benzothiophene, benzofuran, dibenzofuran, indole and carbazole in 54-98% yield.

Methyleneketenes and methylenecarbenes. IX. Thermal rearrangements of Alkyl-and Aryl-acetylenes involving Alkyl- and Aryl-methylenecarbenes

1977 ◽  
Vol 30 (8) ◽  
pp. 1757 ◽  
Author(s):  
RFC Brown ◽  
FW Eastwood ◽  
GP Jackman
Keyword(s):  
Flash Vacuum Pyrolysis ◽  
Vacuum Pyrolysis ◽  
Thermal Rearrangements ◽  
Aryl Acetylenes ◽  
Methylene Carbene

Flash vacuum pyrolysis of 1-(1?-adamantyl)acetylene[2-14C] (780�) gives recovered alkyne which contains 25% of the rearranged product, 1-(1?- adamantyl)acetylene[1-14C]. 1-Ethynyl-1-methylcyclohexane(740�) is converted into toluene and benzene, while evidence for rearrangement of 3,3-dimethylbut-1-yne[2-13C] (790�) and 3-methyl-3-phenylbut-1-yne[2- 13C] (680�) was not obtained before the onset of alternative reactions. These reactions of alkyl-substituted alkynes are discussed in terms of possible methylene carbene intermediates. Similar intermediates may possibly be involved in reactions of arylalkynes. Thus, pyrolysis of 1- ethynylnaphthalene (750�) yields acenaphthylene and of 1-ethynyl-8- methylnaphthalene (750�) yields phenalene. The pathways for the formation of 2-phenyl- and 3-phenyl-indene from (2- methylphenyl)phenylethyne (790�) and of indene from (2- methylphenyl)ethyne (740�) are obscured by facile thermal rearrangements.

Pyrolytic Electrocyclization of Arylmethylidene Derivatives of Glutacononitrile; Synthesis of Dihydroaromatic 1,3-Dinitriles

1998 ◽  
Vol 51 (8) ◽  
pp. 695 ◽  
Author(s):  
Mircea D. Banciu ◽  
Roger F. C. Brown ◽  
Karen J. Coulston ◽  
Frank W. Eastwood ◽  
Tamara Macrae
Keyword(s):  
Aromatic Aldehydes ◽  
Ring Closure ◽  
Secondary Loss ◽  
Flash Vacuum Pyrolysis ◽  
Vacuum Pyrolysis ◽  
Derivatives Of

Condensation of seven aromatic aldehydes (1a–g) with glutacononitrile (2) gave 4-(arylmethylidene)pent-2-enedinitriles (3a–g). Flash vacuum pyrolysis of the dinitriles (3a–g) at 750°/0· 02–0·03 mm gives annulated dihydroaromatic 1,3-dicarbonitriles by electrocyclic ring closure of (3). Fully aromatized products formed by secondary loss of H2 or HCN are also obtained.

Synthesis of Dimethylbutatrienone, (CH3)2C=C=C=C=O, by a Rearrangement-Fragmentation Process and by Direct Elimination

1991 ◽  
Vol 44 (1) ◽  
pp. 87 ◽  
Author(s):  
RFC Brown ◽  
KJ Coulston ◽  
FW Eastwood ◽  
MJ Irvine
Keyword(s):  
Infrared Spectroscopy ◽  
Acid Chloride ◽  
Fragmentation Pathway ◽  
Dienoic Acid ◽  
Fragmentation Process ◽  
Mixed Anhydride ◽  
Argon Matrix ◽  
Flash Vacuum Pyrolysis ◽  
Vacuum Pyrolysis ◽  
Derivatives Of

4-Methylpenta-1,2,3-trien-1-one ( dimethylbutatrienone , Me2C=C=C=C=O) was generated by flash vacuum pyrolysis of precursors derived from 4,4-dimethyl-2-oxotetrahydrofuran-3-ylideneacetic acid (6) and from 4-methylpenta-2,3-dienoic acid (14). Pyrolysis of the mixed trifluoroacetic anhydride and of the acid chloride of (6) and, in poorer yield, of (14) gave 4-methylpenta-1,2,3-trien-1-one which was detected by argon matrix infrared spectroscopy (Vmax 2224, 2216 cm-1) and by reaction with methanol to form methyl 4-methylpenta-2,3-dienoate. The fragmentation pathway for the derivatives of (6) was established by detection of the initially formed propadienone, 4,4-dimethyl-2-oxotetrahydrofuran-3-ylideneethenone, and also by pyrolysis of the trifluoroacetic mixed anhydride (7.L) and the acid chloride (8-L) of 4,4-dimethyl-2-oxotetrahydro(2-13C)furan-3-ylideneacetic acid. The argon matrix spectra of pyrolysates from (7-L) and (8-L) showed bands at 2182 and 2177cm-1 attributed to 4-methyl(1-13C)penta-1,2,3-trien-1-one. 4,4-Dimethyl-3-methylenedihydrofuran-2-one was prepared in 67% yield by flash vacuum pyrolysis of the acid (6).

Synthetic routes to pyrrolizine-1,5-dione derivatives by flash vacuum pyrolysis of amidomethylene derivatives of Meldrum's acid

2009 ◽  
Vol 7 (23) ◽  
pp. 4936 ◽  
Author(s):  
Hamish McNab ◽  
Mark Morrow ◽  
Simon Parsons ◽  
David A. Shannon ◽  
Kirsti Withell
Keyword(s):  
Meldrum's Acid ◽  
Meldrum’S Acid ◽  
Flash Vacuum Pyrolysis ◽  
Vacuum Pyrolysis ◽  
Synthetic Routes ◽  
Derivatives Of

Sulfonyl isocyanides RSO2NC

2017 ◽  
Author(s):  
Curt Wentrup ◽  
Horst Briehl
Keyword(s):  
Ir Spectrum ◽  
Reaction Conditions ◽  
Flash Vacuum Pyrolysis ◽  
Vacuum Pyrolysis

Flash vacuum pyrolysis (FVP) of 5-azido-1-aryltetrazoles results in triple N<sub>2</sub> elimination and formation of aryl isocyanides RNC, which rearrange in part to aroylnitriles RCN under the reaction conditions. Similar FVP of 5-azido-1-arenesulfonyltetrazoles generates a compound absorbing in the IR spectrum (77 K) at 2090 cm<sup>-1 </sup>and assigned the structure of arenesulfonyl isocyanide, ArSO<sub>2</sub>NC <b>11</b>. FVP at temperatures above 600 <sup>o</sup>C results in progressively more nitrile ArSO<sub>2</sub>CN <b>12</b>. Compound <b>11</b> also disappears on warming above -80 <sup>o</sup>C

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