A novel rearrangement of a benzo[b]thiepin derivative

Weintraub, Philip M.; Sill, A. D.

doi:10.1039/c3975000784b

Cited by 9 publications

(1 citation statement)

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“…Thus, the remarkable conversion in Scheme 28 results from the attempt to allylically brominate the thiazepine ( 179).lg9 The bromobenzothiepinone Scheme 28 (180) undergoes novel rearrangements to give the tricyclic products (181) and (182). 190 The first observable silicenium ion (183) is available in solution by the action of trityl perchlorate on the corresponding hydride at -40 to -50°C. '9' Another first is the synthesis of a non-fused borepin (184).…”

Section: % N3mentioning

confidence: 99%

Chapter 11. Heterocyclic chemistry

Meth-Cohn¹,

Smalley²

1975

Annu. Rep. Prog. Chem., Sect. B

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2H-Azirines continue to be used as versatile synthetic reagents. In addition to a full report' on the intramolecular cycloaddition reactions of substituted 2H-azirines noted last year,, further preparative uses have been outlined. Photolysis of 3-crotyl-2H-azirine (1) yields the endo-cyclopropanopyrrole system (2), which, on heating, epimerizes to the more stable exo-form. This reaction involves a cycloaddition of the carbenoid mesomer of a nitrile ylide, and is apparently the first example of this type involving a 1,3-dipolar specie^.^(1)(2)But-2-enyl-2H-azirines are thermally decomposed via vinyl nitrenes, e.g. (3; R = CO,Me) which undergoes a novel 1,4-hydrogen transfer to give an @-unsaturated imine (4; R = C0,Me). A 1,5-H shift followed by electrocyclic ring-closure and loss of ammonia yields the biphenyl (5) (12%) or, by intramolecular Michael addition and loss of methyl acetate, 3-methyl-2-phenylpyridine (58%).4Vacuum pyrolysis of 2-aminoazirines provides a useful source of 2-azabutadienes, e.g. CH,=C(Me)N=CHNMe,, which readily enter into Diels-Alder cycloaddition with suitable dienophiles to give di-and tetra-hydropyridines in practicable yields.'

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Section: % N3mentioning

confidence: 99%