Reactions of 3-aryl-1-(trifluoromethyl)prop-2-yn-1-iminium salts with 1,3-dienes and styrenes

3-Aryl-1-(trifluoromethyl)prop-2-yn-1-iminium triflate salts represent a novel, highly reactive class of acetylenic iminium salts. Herein we present several reactions which are based on the electron-poor acetylenic bond and on the high electrophilicity of the CF3-substituted iminium group. These salts were found to be highly reactive dienophiles in Diels–Alder reactions with cyclopentadiene, 2,3-dimethylbutadiene and even anthracene. At higher temperature, the cycloadducts undergo an intramolecular SE(Ar) reaction leading to condensed carbocycles incorporating a 1-(trifluoromethyl)-1-(dimethylamine)indene ring system. With styrenes and some substituted styrenes, cascade reactions take place, which likely include cyclobutene and several cationic intermediates and mainly yield 2-(1-phenylvinyl)indenes. In a similar reaction cascade, a fulvene derivative was obtained with 1,4-diphenylbutadiene as the substrate.

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ChemInform Abstract: Naphthoquinone Diels-Alder Reactions: Approaches to the ABC Ring System of Beticolin.

ChemInform ◽

10.1002/chin.201505034 ◽

2015 ◽

Vol 46 (5) ◽

pp. no-no

Author(s):

Carsten S. Kramer ◽

Martin Nieger ◽

Stefan Braese

Keyword(s):

Ring System ◽

Diels Alder

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Crystal structures and conformations of two Diels–Alder adduct derivatives: 1,8-bis(thiophen-2-yl)-14-oxatetracyclo[6.5.1.02,7.09,13]tetradeca-2(7),3,5-trien-10-one and 1,8-diphenyl-14-oxatetracyclo[6.5.1.02,7.09,13] tetradeca-2,4,6-trien-10-one

Acta Crystallographica Section E Crystallographic Communications ◽

10.1107/s2056989015001073 ◽

2015 ◽

Vol 71 (2) ◽

pp. 213-216

Author(s):

S. Gopinath ◽

P. Narayanan ◽

K. Sethusankar ◽

Meganathan Nandakumar ◽

Arasambattu K. Mohanakrishnan

Keyword(s):

Crystal Packing ◽

Rotation Axis ◽

Alder Reaction ◽

Ring System ◽

Diels Alder ◽

Compound I ◽

Diels Alder Reaction ◽

Phenyl Rings ◽

Axis Parallel ◽

Alder Adduct

The title compounds, C21H16O2S2(I) and C25H20O2(II), are products of a tandem `pincer' Diels–Alder reaction consisting of [2 + 2] cycloadditions between benzo[c]furan and cyclopentanone. Each comprises a fused tetracyclic ring system containing two five-membered rings (inenvelopeconformations with the O atom as the flap) and six-membered rings (inboatconformations). In addition, two thiophene rings in (I) and two phenyl rings in (II) are attached to the tetracyclic ring system. The cyclopentanone ring adopts atwistedconformation in (I) and anenvelopeconformation in (II). In (I), the thiophene rings are positionally disordered over two sets of sites, with occupancy ratios of 0.901 (2):0.099 (2) and 0.666 (2):0.334 (2). In (II), the oxygen atom of the cyclopentanone ring is rotationally disordered over two sites with an occupancy ratio of 0.579 (4):0.421 (4). The molecular structure of (I) is stabilized by an intramolecular C—H...O hydrogen bond, which generates anS(7) ring motif. In the crystal, the molecules are linkedviaweak C—H...O hydrogen bonds, which generateR22(16) ring motifs in (I) andC(8) chains in (II). In both structures, the crystal packing also features C—H...π interactions. The crystal studied of compound (I) was twinned by non-merohedry. The twin component is related by the twin law [−1 0 0 −0.101 1 −0.484 0 0 −1] operated by a twofold rotation axis parallel to thebaxis. The structure of (I) was refined with a twin scale factor of 0.275 (2).

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Stereoselective total syntheses of (±)-sinularene and (±)-5-epi-sinularene: a general intramolecular Diels–Alder approach to tricyclic sesquiterpenes

Canadian Journal of Chemistry ◽

10.1139/v85-166 ◽

1985 ◽

Vol 63 (4) ◽

pp. 993-995 ◽

Cited By ~ 8

Author(s):

Kazimierz Antczak ◽

John F. Kingston ◽

Alex G. Fallis

Keyword(s):

Double Bond ◽

Methyl Ester ◽

Total Synthesis ◽

Ring System ◽

Diels Alder ◽

Exocyclic Double Bond ◽

Total Syntheses ◽

Methyl Group ◽

Secondary Hydroxyl ◽

Selective Hydrogenolysis

Stereoselective total synthesis of (±)-sinularene and (±)-5-epi-sinularene are described. The sequence employs a "blocked" cyclopentadiene in which the cyclopropane unit also serves as a latent methyl group. Thus intramolecular [4 + 2] cycloaddition of the substituted methyl spiro[2.4]hepta-4,6-dien-1-yl)-2-pentenoate 11 affords 5-benzyloxy-6-isopropyl-8-carbomethoxytetracyclo[5.4.01,7.02,4.02,9]undec-10-ene (12) which after selective hydrogenolysis generates the tricyclo[4.4.01,6.02,8]decane (sinularene) ring system. Removal of the secondary hydroxyl function (Ph3P/CCl4/CH3CN; H2/Pd/C), reduction of the methyl ester (LiAlH4), and introduction of the exocyclic double bond (acetate pyrolysis, 550 °C) completes the synthesis of (±)-sinularene in 14 steps from cyclopentadiene. A parallel series of reactions employing the isopropyl epimer of 12 affords (±)-5-epi-sinularene.

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ChemInform Abstract: A Facile Synthetic Method of ABCD Ring System of Antitumor Alkaloid Camptothecin via Intramolecular Hetero Diels-Alder Reaction.

ChemInform ◽

10.1002/chin.200025209 ◽

2010 ◽

Vol 31 (25) ◽

pp. no-no

Author(s):

Masahiro Toyota ◽

Chiyo Komori ◽

Masataka Ihara

Keyword(s):

Alder Reaction ◽

Ring System ◽

Diels Alder ◽

Synthetic Method ◽

Diels Alder Reaction

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Synthetic studies of zoanthamine alkaloids. Stereoselective synthesis of the ABC ring system of norzoanthamine by an intramolecular Diels–Alder reaction

Tetrahedron Letters ◽

10.1016/s0040-4039(02)00079-5 ◽

2002 ◽

Vol 43 (9) ◽

pp. 1705-1708 ◽

Cited By ~ 27

Author(s):

Mio Sakai ◽

Minoru Sasaki ◽

Keiji Tanino ◽

Masaaki Miyashita

Keyword(s):

Stereoselective Synthesis ◽

Alder Reaction ◽

Ring System ◽

Diels Alder ◽

Diels Alder Reaction ◽

Synthetic Studies ◽

Zoanthamine Alkaloids

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A Thio-Diels−Alder Route to the Azocine Ring System. Total Synthesis of (±)-Otonecine

Journal of the American Chemical Society ◽

10.1021/ja973464e ◽

1998 ◽

Vol 120 (15) ◽

pp. 3613-3622 ◽

Cited By ~ 43

Author(s):

Edwin Vedejs ◽

Rocco J. Galante ◽

Peter G. Goekjian

Keyword(s):

Total Synthesis ◽

Ring System ◽

Diels Alder

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Synthetic studies related to mycobactins. III. Approaches to the synthesis of the cobactin ring system

Australian Journal of Chemistry ◽

10.1071/ch9722429 ◽

1972 ◽

Vol 25 (11) ◽

pp. 2429 ◽

Cited By ~ 7

Author(s):

DSC Black ◽

RFC Brown ◽

AM Wade

Keyword(s):

Primary Amine ◽

Ring Expansion ◽

Hydroxamic Acids ◽

Ring System ◽

Ethyl Benzoate ◽

Yield Reduction ◽

Similar Reaction ◽

Oxidation Reactions ◽

Cyclic Hydroxamic Acids ◽

Synthetic Studies

The synthesis of several seven-membered cyclic hydroxamic acids has been carried out in low yield. Reduction of diethyl 2-hydroxyiminoheptane-l,7-dioate afforded ethyl 1-hydroxy-7-oxohexahydroazepine-2-carboxylate, together with related acyclic products. The cobactin precursor 3-bromo-1-hydroxyhexahydro-azepin-2-one was obtained by the ring expansion of 2-bromocyclohexanone with benzenesulphonohydroxamic acid and also by the peracid oxidation of 6-bromo-7-ethoxy-3,4,5,6-tetrahydro-2H-azepine. The methyl and cinnamyl imidates of hexanolactam were oxidized by peracid to 1-hydroxyhexahydroazepin-2-one, in addition to the related imino- and nitroso-hexanoic esters. In a similar reaction, 1-hydroxypiperidin-2-one was obtained from 2-methoxy-3,4,5,6-tetrahydropyridine. During the course of these oxidation reactions, the intermediate oxaziridines 7-methoxy-8-oxa-1-azabicyclo[5,1,0]octane and 6-bromo-7-ethoxy-8-oxa-1-azabicyclo[5,1,0]octane were isolated and identified. The peraoid oxidation of ethyl N-cyclohexylbenzimidate yielded cyclohexylhydroxylamine and ethyl benzoate in reasonable yields. This reaction suggests a useful method for the conversion of a primary amine into the related hydroxylamine.

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