Carbon/nitrogen rearrangements

Tejedor and coworkers have utilized a combination of two domino processes for a microwave-promoted synthesis of tetrasubstituted pyrroles [344]. The protocol combines two coupled domino processes the triethylamine-catalyzed synthesis of enol-protected propargylic alcohols and their sequential transformation into pyrroles through a spontaneous rearrangement from 1,3-oxazolidines (Scheme 6.183). Overall, these two linked and coupled domino processes build up two carbon-carbon bonds, two carbon-nitrogen bonds, and an aromatic ring in a regioselective and efficient manner. The tetrasubstituted pyrroles could be directly synthesized from the enol-protected propargylic alcohols and the primary amines by microwave irradia-... 

V-phenyIpmprionamidc is found to come directly from alfentanil and not from noralfen-tanil. The mechanism of how the carbon-nitrogen of the spiro center is cleaved has not appeared in the literature. A possible mechanism would entail initial hydroxylation of a ring carbon adjacent to the piperdine nitrogen, followed by elimination of hydroxide to form the imine then rearrangement to the enamine, and finally elimination of the amide as indicated in Figure 4.56. 

The stability of polynitroaliphatic compounds to acids, bases and nucleophiles is often linked to the presence of an acidic o -proton(s) which may allow various resonance structures to lead to rearrangement or decomposition. Additionally, the presence of two or more nitro groups on the same carbon atom greatly increases the susceptibility of the carbon-nitrogen bonds to nucleophilic attack. 

An intermediate aziridinium ion accounts for the observation that alkylations with /S-haloalkyl tertiary amines frequently lead to products with a rearranged carbon-nitrogen skeleton. For example. l-dialkyl-arruno2-jsubstitufc d propanes may form 2-dialkylamino-l-subBtituted... 

In this chapter we shall discuss intramolecular rearrangements to electron-deficient carbon, nitrogen, and oxygen. 

McCarty CG (1970) syn-anti Isomerizations and rearrangements. In Patai S (ed) The chemistry of the carbon-nitrogen double bonds. Wiley, London, chap 9 Bjorgo J, Boyd DR, Watson CG, Jennings WB (1974) J Chem Soc Perkin Trans 2 757 Johnson GP, Marples BA (1984) Tetrahedron Lett 25 3359... 

Raggatt ME, Simpson TJ, Wrigley SK (1999) Biosynthesis of XR587 (Streptopyrrole) in Streptomyces rimosus Involves a Novel Carbon-to-Nitrogen Rearrangement of a Proline-Derived Unit. Chem Commun 1039... 

Similar reactions are known of compounds in which the carbon-nitrogen bond is part of a heterocyclic nucleus.17 18 The oxygen atom of the reactive system may be replaced by a sulfur atom, with, however, some reduction in the tendency toward rearrangement. Allyl p-tolyl sulfide rearranges (XI —> XII) to the extent of 27% (50% based on sulfide not recovered) when subjected to refluxing at 228-264° for four hours.19... 

Photochemical Reactivity of Keto Imino Ethers Type I. Rearrangement and (2+2)-Photocycloaddition to the Carbon-Nitrogen Double Bond... 

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