Dihalocarbene reactions of isobenzofurans

Dehmlow, Eckehard V.; Broda, W.; Schladerbeck, N. H.

doi:10.1016/s0040-4039(01)81612-9

Cited by 6 publications

(1 citation statement)

References 6 publications

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“…Thus dichloro, dibromo, and diiodocarbene react with 6 to afford the appropriate P,P-dihalo-[2-benzoyllstyrenes (10). The authors (10) also proposed initial [2+1] cycloaddition and subsequent rearrangement of vinylcyclopropane systems analogous to 8.…”

Section: Methods Results and Discussionmentioning

confidence: 99%

Azetinone formation is not competitive with intermolecular reactions of a β-lactam-4-ylidene

Zoghbi¹,

Warkentin²

1992

Can. J. Chem.

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.3-Phenoxy-I-phenyl-2-azetidinon-4-ylidene (P-lactam-4-ylidene) 2a, was generated by thermolysis of a spiro-fused p-lactam oxadiazoline precursor (1). Fast 1,2-H migration, a characteristic reaction of singlet carbenes that would convert 2a to 3-phenoxy-1-phenyl-3-azetin-2-one (4a) could not be demonstrated. Added 1, 3-diphenylisobenzofuran (6) did not afford the [4+2] cycloadduct (7) expected from 4a but, instead, the isomeric E-and Z-4-[1-(2-benzoylpheny1)-l-phenyl]-methylene-3-phenoxy-l-phenylazetidin-2-ones (9). Those compounds can be rationalized as the products of rearrangement of first-formed [2+ 11 adducts of 6 and the ylidene. The structure of the Z isomer of 9 was established by means of single crystal X-ray diffraction. Generation of 2a in methanol-d4, either neat or 3.3 M in benzene, afforded the isomeric products of carbene insertion into the OD bond of methanol-d4. Structural isomers expected from addition of methanol-d4 to 4a could not be detected. The results suggest that 1,2-H migration in 2a is relatively slow, with kH 5 1.4 x lo6 s-I at 100"C, which is slower than analogous rearrangement of benzylchlorocarbene by 200-fold or more.MICHEL ZOGHBI et JOHN WARKENTIN. Can. J. Chem. 70, 2792Chem. 70, (1992.La thermolyse d'une oxadiazoline spiro-condensee a une p-lactame (1) conduit au 3-phCnoxy-l-phCnyl-2-azCtidon-4-ylidbne (P-lactam-4-ylidbne) (2a). On n'a pas pu mettre en Cvidence de migration rapide 1,2-H, une reaction caracteristique des carwnes singulets qui permettrait de transformer le compost 2a en 3-phenoxy-1-phCnyl-3-azCtin-2-one (42). L'addition de 1,3-diph6nylisobenzofurane (6) n'a pas permis d'isoler le cycloadduit [4+2] (7) que l'on pourrait attendre 2 partir du produit 4a; on a plut6t obtenu les E-et Z-4-[1-(2-benzoylphCnyl)-1-phCnyl]-m&thylbne-3-phCnoxy-1-phknylazetidin-2-ones isombres (9). On peut rationaliser la formation de ces produits par une transposition des adduits [2+ I ] du produit 6 et de l'ylidkne qui se foment en premier. On a dCterminC la structure de l'isombre Z du composC 9 grdce 2 la diffraction des rayons X par un cristal unique. La gCn6ration du composC 2a dans du methanol-d4, soit a 1'Ctat pur ou en solution 3,3 M dans le benzbne, fournit des produits d'insertion du carbbne dans la liaison OD du methanol-d;. On n'a pas pu ditecter les isombres de structure que l'on pourrait attendre lors de l'addition du methanold4 sur le composC 4a. Les resultats suggbrent que la migration 1,2-H dans le compose 2a est relativement lente, alors que kH 5 1,4 X lo6 s-I, 2 100°C; cette valeur est 200 fois plus faible que celle observke lors de la transposition analogue du benzylchlorocarbbne.[Traduit par la rCdaction]Despite intense interest and activity in the area of p-lactam chemistry (for post-1980 reviews, see ref. I), P-lactam-4-ylidenes, 2 , were described only recently (2). They can be generated efficiently and conveniently by heating spiro-Plactam oxadiazolines (1) at ca. 100°C in solution, Scheme 1, and they have considerable potential for elaboration of the p-lactam syste...

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Section: Methods Results and Discussionmentioning

confidence: 99%

Azetinone formation is not competitive with intermolecular reactions of a β-lactam-4-ylidene

Zoghbi¹,

Warkentin²

1992

Can. J. Chem.

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1,4‐Addition von Dihalogencarbenen an 1,3‐Diene

1985

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Analog entstehen rnit Bromoform die Addukte 2b und 3b im Verhaltnis 70 : 30 in 80% Gesamtausbeute. 2a und 3a lassen sich chromatographisch trennen und durch ihre NMR-Spektren eindeutig charakterisieren (Tabelle 2)[61. Reines 3a erhalt man auch durch Blitzthermolyse des 2a/ 3a-Gemisches in einem Quarzrohr bei 350°C. De Boelelaan 1083, NL-108 1 HV Amsterdam (Niederlande) [**I Diese Arbeit wurde von der Stiftung fiir Chemische Forschung in den Niederlanden (SON) mit einer Subvention (L. W. J.) der niederllndischen Organisation fiir Grundlagenforschung (ZWO) unterstiitzt. 568 0 VCH Verlagsgesellscfiaft mbH. 0-6940 Weinfieim, 1985 0044-8249/85/0707-0568 $ 02.50/0 Angew. Cfiem. 97 (198s) Nr. 7

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1,4‐Addition of Dihalocarbenes to 1,3‐Dienes

Jenneskens

Wolf

Bickelhaupt

1985

Angew. Chem. Int. Ed. Engl.

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bene carbon. Although the resulting interaction (Zr2-06: 2.49(2) A) is weak (and certainly unstable in solution) in comparison with that in the metallocyclic five-memberedring skeleton (Zrl-01 2.16(2) A), it is sufficient to connect the monomeric zirconiumoxycarbene-W(CO), units in the solid specifically to give a polymeric helical molecular chain. The two independent units of 4a together form the repeating structural unit of the helix (see Fig. 2). Solvent molecules (in this case, toluene) occupy positions between the chains in a disordered fashion. However, the incorporated solvent is only weakly bound. It is rapidly released, with destruction of the crystal structure, upon passing a stream of inert gas over the solid. Fig. 2. Crystal structure of 4a: a view of the helical molecular chains. For simplification, only the -Zr(C,O)-W-(C0)-skeletal units are drawn.The formation of the polymeric helix structure of 4a in the solid state is possibly an indication of the importance of a dipolar resonance structure 4a' in describing the properties of this zirconiumoxycarbene complex:[91 The unusually electrophilic Zr center is attacked by the negative end of the dipole, the oxygen of the carbonyl group, in a manner that is typical1"] of a carbonylmetalate ion.Research (SON) with a grant (L. W. J.) from the Netherlands Organization for the Advancement of Pure Research (ZWO). Angew. Chem. lnt. Ed. Engl. 24 (1985) No. 7 0 VCH Verlngsgesellscha/c mbH. 0-6940 Weinheim, 1985 0570-0833/85/0707-0585 $ 02.50/0

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Dihalocarbene reactions of isobenzofurans

Cited by 6 publications

References 6 publications

Azetinone formation is not competitive with intermolecular reactions of a β-lactam-4-ylidene

Azetinone formation is not competitive with intermolecular reactions of a β-lactam-4-ylidene

1,4‐Addition von Dihalogencarbenen an 1,3‐Diene

1,4‐Addition of Dihalocarbenes to 1,3‐Dienes

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