Our Research
HomeWe are interested in different aspects of organic synthesis with a strong attention on the development of new synthetic methods. A major target is the rapid construction of complex structure from simple, readily available starting materials to optimized atom-, step- and redox- efficiency. These materials should be readily obtainable not only in quantities in low prices but also in structural diversity.
We focus on the use of molecular oxygen as
oxidant; iodine, iron as well as their simple salts as catalysts; and elemental
sulfur as a direct sulfur building-block for organosulfur compounds.
Specifically, we target the application of simple and practical reaction conditions: Simple heating and simple mixing in standard glasswares. We strive to develop more straightforward synthetic sequences to maximize atom-, step-, and redox- efficiency.
Multicomponent Redox Reactions with Elemental Sulfur
We target the development of new methods using directly elemental sulfur as a sulfur building block for multicomponent redox reactions. This strategy allows the access to a wide range of sulfur-containing compounds, including thioamides, thioureas, and benzothiazoles. Elemental sulfur is an excellent candidate for such transformations due to the following reasons:
- Inexpensive
- Non-toxic, easy to handle
- High atom efficiency
- Polyvanlent: sulfur, beside its
role as buiding-block, can act as oxidizing and/or reducing agent
Iron-Sulfur Cluster as Novel Redox Catalysts
Simultaneously, we seek to
develop new catalysts for redox condensation reaction in which an oxidizing reaction
partner condenses with a reducing one, leading to a condensed product without
prior redox step. As a representative example, a classical approach these
compounds consists in condensing 2-amino/hydroxy anilines 4 with a carboxylic acid or derivatives 5. This approach, although extensively used, cannot be considered as
an atom economical transformation because both of the starting materials are
usually obtained by two opposite reactions:
(i) anilines 4 from the
reduction of the corresponding nitrobenzenes 1 (6e– transfer);
(ii) carboxylic acids 5 from the
oxidation of their lower oxidation degree parent compounds 2 such as aldehydes,
primary alcohols or even methyl derivatives (2e–, 4e–, or 6e– transfer
respectively).
A catalyst capable of effecting
a direct hydrogen transfer from 2 to 1 would be highly desirable because three
processes oxidation, reduction and condensation are carried out in only one operation.
The bio-inspired Iron-Sulfur cluster catalyst were among our first tool for such transformation.
Nature has used this kind of
catalyst in a wide variety of enzymes for a wide range of redox transformations:
carbon metabolism, nitrogen fixation,
photosynthesis, hydrogenation... Its role can be compared to a
capacitor in an electric circuit which can store and release reversibly
electrons in function of external voltage, thus serve as electron transfer
catalysts. These clusters can be formed by simply mixing elemental sulfur and metallic iron as well as their simple salts.
New Guanidination Methods
Guanidine is a frequently
encountered motif in marine natural products issued from marines sponges. Such
compounds are widely reported to exhibit a wide range of interesting biological
activities.
We
strive to find new practical
methods for direct incorporation of this moiety into carbon skeletons.
These methods can be applied to the syntheses of simplified analogs of
benzosceptrins, natural products isolated by our group which are
interesting synthetic and bioactive targets.