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Enynoindoles undergo metathesis reactions leading to structures related to alkaloids. The formation of an unexpected product is reported and discussed

The synthesis of indoles bearing alkenyl and alkynyl moieties in different positions of the nucleus is described. These compounds are used as substrates for the intermolecular Pauson-Khand reaction leading to tetracyclic cyclopentenones with formation of additional five- to seven-membered rings. Products are related to alkaloids such as mitosenes, clausines, ergotamines, or apogeissochizines.

Lithiation at C4 of the indole nucleus is readily directed by several functional groups. The 4-substituted indoles thus obtained are transformed into suitable substrates for metathesis reactions. Ring-closing metathesis effected on these compounds lead to skeletons related to several indole alkaloids.

The synthesis and evaluation of new ligands for the H3 receptor of histamine is described. These new compounds are diimidazopyridine derivatives readily prepared by a condensation reaction of spinacine and isocyanates.

The RCM metathesis reaction catalyzed by Grubbs’ ruthenium catalyst is used with a series of 1,2-disubstituted indoles leading with excellent yields to tricyclic compounds. When applied to 1-allyl-2-vinylindoles this methodology allows a new entry to the mitosene skeleton.

Seven membered rings are obtained with good yields by intramolecular Pauson–Khand reactions of some aromatic compounds.

The synthesis and evaluation of new ligands for the H3 receptor of histamine is described. These new compounds are diimidazopyridine derivatives readily prepared by a condensation reaction of spinacine and isocyanates.

The RCM metathesis reaction catalyzed by Grubbs’ ruthenium catalyst is used with a series of 1,2-disubstituted indoles leading with excellent yields to tricyclic compounds. When applied to 1-allyl-2-vinylindoles this methodology allows a new entry to the mitosene skeleton.

Lithiation at C4 of the indole nucleus is readily directed by several functional groups. The 4-substituted indoles thus obtained are transformed into suitable substrates for metathesis reactions. Ring-closing metathesis effected on these compounds lead to skeletons related to several indole alkaloids.

A convenient synthesis of indoles bearing allyl, ethynyl, and/or propargyl moieties is described starting from indole or indole-2-carboxylic acid.

The synthesis of indoles bearing alkenyl and alkynyl moieties in different positions of the nucleus is described. These compounds are used as substrates for the intermolecular Pauson-Khand reaction leading to tetracyclic cyclopentenones with formation of additional five- to seven-membered rings. Products are related to alkaloids such as mitosenes, clausines, ergotamines, or apogeissochizines.

There are still some synthetic chemists who hesitate to use metal-mediated or -catalysed reactions. The Pauson–Khand reaction (PKR) is a powerful transformation that has now been sufficiently well developed to be routinely considered when planning a synthesis, especially of polycyclic complex molecules. This tutorial review aims to encourage the use of this process explaining the best ways of performing a PKR both in the stoichiometric and the catalytic version, showing the scope of the process and its limitations. Additionally, asymmetry can be introduced in the reaction using several strategies, which will be discussed. The most recent examples of the synthetic applications of the PKR in natural product synthesis will give the reader an idea of the great usefulness of this reaction.

Pauson−Khand reactions are carried out with different substituted aromatic enynes, yielding tricyclic cyclopentenones related to natural products such as chromenes. Enynes are easily obtained in a two-step approximation from the corresponding salicylaldehydes. The reaction is promoted by dissolved TMANO (trimethylamine N-oxide) and/or 4 A molecular sieves. This new way of induction for the Pauson−Khand reaction increases yields remarkably, allowing the reaction of some substituted alkenes which fail to react in the absence of the zeolite. Isomerization of the double bond of the cyclopentenone ring is observed except when nonterminal triple bonds are used. For trisubstituted alkenes, an interrupted Pauson−Khand process is observed with moderate yields.

Seven membered rings are obtained with good yields by intramolecular Pauson–Khand reactions of some aromatic compounds.

The Pauson−Khand reaction still has a relatively low scope with respect to the used carbon skeleton, while yields are low in many other cases. We have observed that the addition of molecular sieves improves yields remarkably. Experimental protocol is extremely easy, and it has been applied to several substrates including the less favorable ones.

A convenient synthesis of indoles bearing allyl, ethynyl, and/or propargyl moieties is described starting from indole or indole-2-carboxylic acid.