The preparation of new heterocyclic systems by conventional ways is normally a hard work that implies many synthetic steps and expensive starting materials. Even more, many heterocyclic systems, being predictably stable, are impossible to be prepared because the synthetic approach simply does not exist. There is a very different approach to get new heterocyclic systems that uses simple organic starting materials (tertiary amines, alicyclic oximes) bearing a nucleophilic nitrogen which generates reactive intermediates, subsequently trapped by a inorganic reagent, disulfur dichloride (S2Cl2). In general, trapping of intermediates is followed by extensive dehydrogenation and chlorination to give new intermediates that can be trapped by selected nucleophiles on the way to stable final products.1-2 A good combination of reagents and reaction sequences permits the preparation of heterocycles that imply up to fifteen different steps all working sequentially in a one-pot reaction. The best example of this chemistry is the reaction of N-ethyldiisopropylamine (Hünig’s base), with disulfur dichloride.3-4 The first step is a slow oxidation of the amine to an immonium salt by a combination of disulfur dichloride and DABCO (diazabicyclo[2.2.2]octane).

The rhodium(II)-catalyzed reaction of a-diazo ketones bearing tethered alkyne units represents a new and useful method for the construction of a variety of substituted cyclopentenones. The process proceeds by addition of the rhodium-stabilized carbenoid onto the acetylenic pi-bond to give a vinyl carbenoid intermediate. The resulting rhodium complex undergoes a wide assortment of reactions including cyclopropanation, 1,2-hydrogen migration, CHinsertion, addition to tethered alkynes and ylide formation. When 2-alkynyl-2-diazo-3-oxobutanoates were treated with a Rh(II)-catalyst, furo[3,4-c]furans were formed in excellent yield.

a -Amino and a -hydroxy acids and their derivatives play an important role in organic synthesis, especially in asymmetric synthesis as chiral synthons, chiral auxiliaries, and resolving agents [1-3]. In the course of our studies of heteroaryl substituted a -amino and a -hydroxy acids and their derivatives we have prepared easily accessible 2-acylamino-3-dimethylaminopropenoates, 2-(O-substituted hydroxy)-3- dimethylaminopropenoates, and 2-ethenylamino-3-dimethylaminopropenoates, masked a -formyl-a -amino- and a - formyl-a -hydroxy acids, and their derivatives. They have turned out to be excellent reagents for the preparaton of a variety of heterocyclic systems with an amino or hydroxy acid structural element incorporated or partially incorporated into the newly formed heterocyclic ring [4]

This review reports some novel (or considerably improved) methods of the synthesis of aromatic iodides, (dichloroiodo)arenes, (diacetoxyiodo)arenes, iodylarenes, diaryliodonium salts as well as some facile, oxidative anion metatheses in crude diaryliodonium halides and, for comparison, potassium halides. All these new results were obtained in our laboratory within the past decade (1990- 2000). A full list of our papers dealing with the organic iodine(I, III and V) chemistry, covering exlusively the aromatic derivatives, is also submitted (Refs. 1-18)

A new class of enantiopure b-aminoalcohols having 1,1’-binaphthyl skeleton, and chiral only by atropisomerism, has been prepared and tested as catalytic precursors in the asymmetric addition of diethylzinc to aromatic aldehydes. The aldehydes were quickly and cleanly (99% yield) transformed in the corresponding alcohols with ee up to 87%.

A series of imides with two chirality axes have been synthesized. Comparatively low activation barriers to isomerisation and, at the same time, high melting points lead to interesting behaviors of these compounds: whereas thermodynamic equilibria of nearly 50:50 diastereomeric ratios were reached rapidly in solution at 110°C, ratios up to 99:1 in favor of one diastereomer have been observed after prolonged heating above the same temperature of the mixture of diastereomers in the solid state. Crystallographic and differential scanning calorimetric (DSC) techniques have been used to support these studies and their interpretation.

Oxazolidine moieties are widely recognized as very useful chiral auxiliaries in asymmetric reactions,1 and chiral epoxides have been frequently involved in the design of strategies for the achievement of stereocontrol.2 However, only few examples reported in literature,3 combine the influence in the same substrate of both epoxide and oxazolidine moieties, although in any case related with intramolecular reactions. As a part of our ongoing research program aimed at the synthesis of biologically relevant hydroxylated amino acids,4 we wish to report an easy strategy which allows the stereoselective preparation of 4,5-disubstituted oxazolidinones 5, based on the use of the homochiral epoxy oxazolidines derived from L-Serine, which could be precursors of b,gdihydroxy- a-amino acids (Scheme 1).

Lewis acid modulated reactions play a very important role in organic synthesis as they provide versatile intermediates, sometimes dictating the stereochemistry of the products (1). Nitrones are substrates rather sensitive to Lewis-acid modulation as we have amply demonstrated during the last years (2) in nucleophilic additions to chiral nitrones. For instance, it has been demonstrated in our laboratory that by employing either ZnBr2 or Et2AlCl, one can produce hydroxylamines with either syn or anti stereochemistry (with respect to the alfa group), respectively (3). 1,3-Dipolar cycloaddition reactions with nitrones are also susceptible to be influenced by the presence of Lewis acids. In fact, Lewis acids catalyzed nitrone cycloadditions have been extensively studied (4). Kanemasa and Tsuruoka have suggested the participation of nitrone-MgBr2 complexes in some cycloaddition reactions with allylic alcohols (5). The scope and limitations of chiral Mg(II) and Cu(II) complexes on the selectivity of cycloaddition of nitrones with alkenes have been studied by Jorgensen and coworkers (6). Activation of nitrones by chiral Lewis acids towards cycloadditions with electron-rich alkenes have also been reported

The research enterprise in our laboratory is based on the premise that many conceptually simple chemical transformations can be envisioned which have not yet been reduced to practice. This account presents the discovery and current state of optimization of a new reaction which was recently discovered in our laboratories, namely the tungsten carbonyl-catalyzed endo-selective cycloisomerization of alkynyl alcohols to dihydropyrans, and applications to the stereoselective synthesis of disaccharide substructures of digitoxin, landomycin, and mithramycin natural products.

Previous work on differently substituted carbostyrils [1-3] has shown that only some especially substituted molecules of this substance class show interesting fluorescence properties. However, in contrast to the widely used oxa analogue coumarins strong fluorophors are scarce. Therefore principle strategies have been investigated, which substituent properties are important. What makes a carbostyril to be a good fluorophor? - Donor substituents in positions 6 and 7 - a trifluoromethyl group in position 4 Experimental and theoretical data have shown that the position 7 influences properties like absorption and quantum yield, whereas position 6 is connected to absorption wavelength. A strong acceptor substituent in position 4 gives a significant bathochromic shift and increases the quantum yield in most of the investigated molecules.