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A new tandem reaction sequence has been developed for the synthesis of 2‐phosphono pyrroles. The sequence consists of ring‐closing enyne metathesis of a substituted aminophosphonate, containing a terminal alkyne and an internal alkene, in combination with in situ oxidation of the produced 3‐pyrrolines using tetrachloroquinone. By analyzing the formation of the end and certain byproducts, taking into account the difference in reactivity of different substrates and carefully studying spectroscopic data, it was found that the reaction proceeds by means of the “yne‐then‐ene” pathway. During the initiation phase, a new ruthenium carbene is formed which continues the propagation cycle.

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When a mixture of a pyroglutamate and an isocyanate in THF is treated with NaH, a ring transformation occurs leading to functionalised hydantoins. The novel reaction involves a ring‐closing ring‐opening sequence providing a new and straightforward access to an interesting class of heterocyclic compounds. Furthermore, starting from pyroglutamates allows the synthesis of highly substituted hydantoins under very mild conditions. This ring transformation in combination with ring‐closing metathesis is used in a four‐step reaction sequence for the synthesis of multi‐functionalised bicyclic hydantoin derivatives.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

[reaction: see text] Perhydro-1,3-diazepine-2,4-diones are rare and can only be prepared, up to now, by special methods. A new one-step protocol was developed, comprising N-carbamoylation using an isocyanate followed by intramolecular ring expansion. This new methodology provides a straightforward access to this interesting seven-membered skeleton.