Synthesis of enantiopure 2-C-glycosyl-3-nitrochromenes.

A novel methodology has been developed to obtain enantiopure 2-C-glycosyl-3-nitrochromenes. First, (Z)-1-bromo-1-nitroalkenes were prepared from the corresponding sugar aldehydes through a sodium iodide-catalyzed Henry reaction with bromonitromethane followed by elimination of the resulting 1-bromo-1-nitroalkan-2-ols. In the next step, reaction of the sugar-derived (Z)-1-bromo-1-nitroalkenes with o-hydroxybenzaldehydes afforded enantiopure (2S,3S,4S)-3-bromo-3,4-dihydro-4-hydroxy-3-nitro-2H-1-benzopyrans, which, upon SmI2-promoted ß-elimination, yielded chiral enantiopure 2-C-glycosyl-3-nitrochromenes.

General metal-free Baeyer-Villiger-type synthesis of vinyl acetates.

Oxone, a cheap, stable, and nonhazardous oxidizing reagent, transforms α,ß-unsaturated ketones of defined stereochemistry into their corresponding vinyl acetates through a Baeyer-Villiger reaction. This process is general and straightforward, tolerating a wide range of functional groups.

The first sequential reaction promoted by manganese: complete stereoselective synthesis of (E)-alpha,beta-unsaturated esters from 2,2-dichloroesters and aldehydes.

Alpha,beta-unsaturated esters were obtained with complete control of stereoselectivity utilizing a sequential reaction of dichloroesters with a variety of aldehydes, promoted by active manganese. This methodology is generally applicable, and the C-C double bond can be di- or trisubstituted. A mechanism based on a successive aldol-type reaction/beta-elimination is proposed to explain these results.

Total selective synthesis of enantiopure O1-acyl-3-aminoalkane-1,2-diols by ring opening of aminoepoxides with carboxylic acids.

[reaction: see text] Synthesis of (2R,3S)- or (2S,3S)-O1-acyl-3-aminoalkane-1,2-diols by ring opening of enantiopure (2R,1'S)- or (2S,1'S)-2-(1-aminoalkyl)epoxides 1 or 2, with carboxylic acids in the presence of BF3 x Et2O and chlorotrimethylsilane, is described. The conversion takes place with total selectivity and in good yield. In addition, (2R,3S)-O,O-diacyl-3-aminoalkane-1,2-diols 3 were also prepared from reaction of (2R,1'S)-2-(1-aminoalkyl)epoxides 1 with carboxylic acids under the same reaction conditions and without chlorotrimethylsilane. Mechanisms to explain both transformations are proposed.

A novel cadmium aminophosphonate: X-ray powder diffraction structure, solid-state IR and NMR spectroscopic determination of the fine structure of the organic moieties.

A new divalent cadmium phosphonate, Cd2Cl2(H2O)4(H2L), has been synthesized from the ethylenediamine-N,N'-bis(methylenephosphonic acid) (H4L). The obtained microcrystalline compound has been characterized by solid-state IR spectra and 13C, 31P, and 113Cd CP MAS NMR. The static 13P NMR spectra have been also recorded to give the delta11, delta22, and delta33 chemical shift parameters for both compounds. The spectral data, collected for Cd2Cl2(H2O)4(H2L), are in an agreement with its X-ray powder diffraction structure solved with the cell dimensions a = 16.6105(10), b = 7.1572(4), and c = 6.8171(4) A and beta = 98.327(4) degrees. The octahedral coordination sphere of the cadmium atoms consists of two phosphonate oxygen atoms, two water oxygen atoms, and the two chlorine atoms. Cadmium atoms are bridged by the chlorine atoms forming four-membered rings. The phosphorus atoms exhibit a tetrahedral coordination with two oxygen atoms bonded to the cadmium atoms with P-O distances of 1.503(10) and 1.504(10) A. The third oxygen atom, showing a longer P-O distance (1.546(9) A), is not bonded to the metal center, nor is it bonded to a proton. The combined IR and NMR proton-phosphorus cross-polarization kinetic data together with the X-ray data confirm that the cadmium phosphonate has the zwitterionic structure (NH2(+)CH2P(O2Cd2)O-) similar to the initial aminophosphonic acid H4L.

Transformation of alpha,beta-epoxyesters into 2,3-dideuterioesters promoted by samarium diiodide.

An easy and general sequenced elimination/reduction process by means of samarium diiodide, in the presence of D(2)O, provides an efficient method for synthesizing 2,3-dideuterioesters 2. The reaction can be also carried out in the presence of H(2)O instead of D(2)O, yielding the corresponding saturated esters 4. Other deuterated esters have been also obtained. A mechanism to explain this synthesis has been proposed.

Sequential elimination-cyclopropanation reactions promoted by samarium: highly diastereoselective synthesis of cyclopropylamides.

trans-Cyclopropanamides were obtained, in high yield, from 2-chloro-3-hydroxyamides by a sequenced elimination-cyclopropanation process promoted by Samarium/diiodomethane or Samarium diiodide and Samarium/diiodomethane.