Electrocyclic aromatic substitution by the diazo group. Part 5. The reactions of α-(2-arylthienyl)diazoalkanes

Munro, David P.; Sharp, John T.

doi:10.1039/p19840000571

Cited by 13 publications

(12 citation statements)

References 4 publications

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“…Pure (E)-2b was obtained by isomerization of the (E)/(Z) mixture using iodine. [14] Formylation of 2 to yield the 2-(alkenyl)benzaldehydes 3 was accomplished by metalation with n-butyllithium and subsequent addition of dimethylformamide, also according to a procedure given by Hibino et al [13] In the third step, condensation with benzylamine in the presence of molecular sieves yielded the 2-(alkenyl)benzaldimines 4aϪd (Scheme 2). [15] Condensation with allylamine produced the imines 4eϪg (Scheme 3).…”

Section: Resultsmentioning

confidence: 99%

“…When necessary, the experiments were carried out with complete exclusion of moisture (argon, septum-syringe technique) in glassware that had been thoroughly dried by repeated heating under argon and subsequent evacuation. The 2-(alkenyl)bromobenzenes 2a, [13] 2b, 2d, [14] 2c [26] were prepared by Wittig olefination of 2-bromobenzaldehyde (1) in accordance and analogy to literature procedures. Pure (E) isomer (E)-2b was obtained upon isomerization of (E,Z)-2b in the presence of iodine.…”

Section: Resultsmentioning

confidence: 99%

“…Pure (E) isomer (E)-2b was obtained upon isomerization of (E,Z)-2b in the presence of iodine. [14] The 2-alkenylbenzaldehydes 3a, [13] 3b, 3d, [14] 3c [27] were prepared by formylation of the compounds 2aϪd using n-butyllithium and dimethylformamide according to a literature procedure. [13] For the preparation of (E)-3b pure (E)-2b was used.…”

Section: Resultsmentioning

confidence: 99%

“…0.73 g (5.0 mmol) of (E)-3b [14] and 0.53 g (5.0 mmol) of benzylamine were mixed together in dry dichloromethane (20 ml) and stirred in the presence of molecular sieves (4 Å ) at room temperature for 16 h. The molecular sieves were removed by filtration and washed with dichloromethane (20 ml [16] The crude product was purified by column chromatography (silica gel; petroleum ether/ethyl acetate, 10:1). Two diastereomeric isomers (3R*,4S*,5S*)-6b (120 mg, 48%) and (3R*,4R*,5R*)-6b (35 mg, 0.14 mmol, 13%) were isolated as colorless oils.…”

Section: (E)-benzyl(2-propenylbenzylidene)amine [(E)-4b]mentioning

confidence: 99%

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4,5‐Dihydro‐3H‐benzo[c]azepines from 1,7‐Electrocyclization Reactions of 2‐Aza‐4,5‐benzoheptatrienyllithium Compounds

Gerdes¹,

Sagar²,

Fröhlich³

et al. 2004

Eur J Org Chem

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Various differently substituted (2‐alkenylbenzylidene)amines 4b−d gave, upon deprotonation with amide bases and addition of an electrophile, the respective 4,5‐dihydro‐3H‐benzo[c]azepines 6a−k in moderate to good yields. The imines 4 are easily accessible from 2‐bromobenzaldehyde (1) by Wittig olefination, formylation with DMF, and subsequent condensation with benzylamine. The ring‐closure reaction is interpreted as an anionic 1,7‐electrocyclization reaction involving benzo‐annulated 2‐azaheptatrienyllithium compounds. This reaction, and the subsequent addition of the electrophiles, proceed with excellent diastereoselectivity, determined by the (E) or (Z) configuration of the imines 4b−d. The corresponding allylimines 4e,f do not give ninemembered heterocycles 7, but rather the corresponding 3‐vinyl‐4,5‐dihydro‐3H‐benzo[c]azepines 6l,m. Molecular structures of several compounds 6 in the solid state were determined by X‐ray crystallography, including the structure of a 14‐membered ring dimer 8. High‐level quantum chemical calculations on model anions concerning structures and relative energies of possible intermediates and transition states support the pericyclic mechanism suggested for the ring‐closure reaction. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: (E)-benzyl(2-propenylbenzylidene)amine [(E)-4b]mentioning

confidence: 99%

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4,5‐Dihydro‐3H‐benzo[c]azepines from 1,7‐Electrocyclization Reactions of 2‐Aza‐4,5‐benzoheptatrienyllithium Compounds

Gerdes¹,

Sagar²,

Fröhlich³

et al. 2004

Eur J Org Chem

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“…As with the thermolysis of the unprotected aldehyde (la), the azide (6a) gave two products on heating in xylene. The major product (53%) was the desired 4-substituted indole (Ma), whilst the minor product was identified as the isoquinoline (20), presumably formed oia the insertion product (21). The protected azidoketone (6b), which contains no reactive benzylic hydrogen for insertion, gave the 4-substituted indole (19b) in quantitative yield.…”

Section: Coz Me C02mementioning

confidence: 99%

Vinyl azides in heterocyclic synthesis. Part 6. Synthesis of isoquinolines by intramolecular aza-Wittig reaction

Hickey¹,

Mackenzie²,

Moody³

et al. 1987

J. Chem. Soc., Perkin Trans. 1

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Azidocinnamates containing ortho-carbonyl substituents are versatile intermediates for heterocyclic synthesis. lsoquinolines (8) and (9) are formed under mild neutral conditions by intramolecular azaWittig reactions of iminophosphoranes, readily derived from azides (1 ) and (2), respectively, with triethyl phosphite. The azafluoranthene (10) can also be prepared from the azide (3) via the isolable iminophosphoranes (11) and (12). Thermolysis of the azides (1) in toluene or xylene gives the 4-substituted indoles (13) in varying yield (Table 2). Similarly the indoles (14) and (19) are formed from the azides (3) and (6a and b) respectively.Compounds containing the isoquinoline nucleus are widely distributed in Nature-more than 1 OOO isoquinoline alkaloids have now been identified3-and since the isolation of isoquinoline itself in 1885 enormous effort has been devoted to the synthesis of this bicyclic aromatic system.495 However, the most widely used methods of isoquinoline synthesis, such as the classic Bischler-Napieralski, Pictet-Spengler, and PomeranzFritsch reactions, require relatively harsh acid or dehydrating conditions to effect ring closure, and since they usually involve electrophilic attack on a benzene ring, the reaction is greatly facilitated by the presence of electron-donating substituents. Indeed, in the absence of such substituents, ring closure often fails completely or proceeds in low yield under forcing conditiom6 Surprisingly few attempts to solve the 'activation' problem in isoquinoline synthesis have been reported, although recently the methylthio group has been proposed as an easily removable activating group which allowed the preparation of isoquinolines lacking substituents in the carbocylic ring.6An alternative approach is to use a ring closure method which does not involve electrophilic attack on a benzene ring, and one such method, developed independently by Woodward and by Miller,' involves ozonolysis of an indene to give a homophthalaldehyde derivative which on treatment with aqueous ammonia gives the fully aromatic isoquinoline directly. Although this simple but elegant approach can be used to prepare isoquinolines containing electron-withdrawing substituents, its generality is somewhat limited by the availability of the starting indenes. We now report the full details of a new isoquinoline synthesis based on the intramolecular aza-Wittig reaction, which enables ring closure to occur under mild, neutral conditions. Although a few examples of this reaction are known,9 it has not been applied to the synthesis of isoquinolines before.' Results and DiscussionThe substrates for the intramolecular am-Wittig reaction were the azidocinnamates (la-),(2), and (3) containing orthocarbonyl substituents. Provided that the group R' contained no X-C-H bonds, the azides could be prepared directly by condensation of the appropriate benzaldehyde with methyl or ethyl azidoacetate under basic conditions. Thus the azides (la) and (1 b) were obtained from 2-formylbenzophenone O and commercially available 2...

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Syntheses, Reactions, and Physical Properties of Bithienyls and Polythienyls and Closely Related Compounds

Håkansson

1992

Chemistry of Heterocyclic Compounds: A Series of Monographs

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Electrocyclic aromatic substitution by the diazo group. Part 5. The reactions of α-(2-arylthienyl)diazoalkanes

Cited by 13 publications

References 4 publications

4,5‐Dihydro‐3H‐benzo[c]azepines from 1,7‐Electrocyclization Reactions of 2‐Aza‐4,5‐benzoheptatrienyllithium Compounds

4,5‐Dihydro‐3H‐benzo[c]azepines from 1,7‐Electrocyclization Reactions of 2‐Aza‐4,5‐benzoheptatrienyllithium Compounds

Vinyl azides in heterocyclic synthesis. Part 6. Synthesis of isoquinolines by intramolecular aza-Wittig reaction

Syntheses, Reactions, and Physical Properties of Bithienyls and Polythienyls and Closely Related Compounds

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