Alessandro Degl'Innocenti

A new stereoselective synthesis of chiral γ-functionalized (E)-allylic amines

Abstract Chiral t -Boc protected propargylic amines have been obtained starting from aminoaldehydes derived from natural aminoacids. Stannylcupration of these substrates affords an easy regio- and stereocontrolled route to the corresponding γ-stannylated ( E )-allylamines which are useful intermediates for the synthesis of the corresponding γ-funtionalized allylic systems.

Chemical and spectroscopic characterization of the humic substances from sandstone-derived rock fragments

The characterization of soil organic matter, and of humic substances in particular, has always been made on fine earth, i.e., the <2-mm fraction. The fraction larger than 2 mm, known as rock fragments or skeleton, is commonly discarded. We have extracted the humic acids (HAs) and fulvic acids (FAs) from fine earth, rock fragments, and rock fragments washing (i.e. the fine material adhering to the rock fragments) of the upper forest soil horizons, A1 and A2. The substances were characterized using wet-chemical analyses, FT-IR, and liquid state 13C NMR spectroscopies. HAs of the rock fragments have higher N and H content, paraffinic chains, aliphatic-OH, and highly substituted aromatic groups than those of the fine earth. These features indicate that carbohydrates, lipids, and proteinaceous residues are incorporated in the humic acids of the rock fragments. The fresh biological material residues present in the structure of the skeleton HAs may be attributable to: (i) the selective preservation from microbial and chemical attack offered by the skeletal environment; (ii) the more rapid cycling of the organic matter inside the rock fragments compared with that of the fine earth. The FAs show greater homogeneity than the HAs, probably because of their mobility among the different soil compartments. However, the FAs of the rock fragments have more carboxyl and acidic-OH groups than found in the fine earth. Greater differences are also observed between the two horizons. The FAs extracted from the A2 horizon show less mineralization than those from the A1 horizon. The humic substances extracted from the rock fragments washing show characteristics more similar to those of the skeleton than to those of the fine earth. This suggests that most rock fragments washing originate from the weathering of the rock fragments and, therefore, may be regarded as an intermediate phase between the skeleton and the fine earth.

Fluoride ion induced reactions of organosilanes with electrophiles

Abstract Benzyl- 4-picolyl- and phenylallyl(trimethyl)silanes react with electrophiles in the presence of KF/18-crown-6 or silica-TBAF under mild conditions.

Bis(trimethylsilyl)sulfide based thionation of carbonyl compounds : synthesis of thioketones

Abstract A wide range of thioketones may be conveniently obtained by silyl triflate promoted bis(trimethylsilyl)sulfide thionation of ketones.

An ESR investigation of some paramagnetic species derived from aroylsilanes, aroylgermanes and aroylstannanes

Abstract The spin adducts between Group IVB organometallic radicals (M.R 3 , M = Si, Ge, Sn) and benzoyltriphenylsilane, benzoyltriphenylgermane and benzoyltriphenylstannane have been investigated by ESR spectroscopy. Secondary radical species were detected when acetyltrimethylsilane was used, and their nature and origin are discussed. The radicals formed upon reduction with alkali alkoxides in polar solvents have also been investigated.

Base-promoted elaboration of aziridines

The base-promoted isomerization of aziridines to allyl amines is still an almost unknown reaction. However, the use of superbasic reagents has shown to be able to promote a regio- and stereoselective conversion of monocyclic and bicyclic sulfonyl aziridines. Moreover, the use of alkoxy substituted aziridines opens new routes to non-natural α- and β-amino acids.

Stannylcupration of γ-heterosubstituted acetylenic esters: A new route to 4-stannylated five membered N- and O- heterocycles

Abstract 4-Tributylstannyl,2-(5H)-furanone and pyrrolone have been prepared in good yields by addition of mixed stannylcuprate reagent on γ-amino and γ-hydroxy acetylenic esters. The use of these compounds as useful intermediates for the selective functionalization of these heterocyclic rings is discussed.

Synthesis of polyfunctionalized acylsilanes via propenoyltrimethylsilane

Abstract Propenoyltrimethylsilane (1) reacts with silylated nucleophiles to yield the β-functionalised silyl enol ethers of acylsilanes. Further “in situ” reaction of these compounds affords an easy entry into the class of polyfunctionalised acylsilanes.

2-Trimethylsilyl-1,3-dithiolane as a masked dithiolane anion

Abstract 2-Trimethylsilyl-1,3-dithiolane, easily obtainable through transthioacetalization of corresponding silylated acetals, can be efficiently reacted, under fluoride-ion catalysis, with different organic electrophiles, leading to a general and mild functionalization protocol. This reactivity discloses the ability of compound 3 to act as a masked dithiolane anion.

Stereoselective synthesis of (R)-(−)-2,2-dimethyl-3-t-butoxycarbonyl-4-ethynyl-oxazolidine: a chiral building block for the synthesis of a new class of substituted alkynes

Abstract (R)-(-)-2,2-Dimethyl-3-t-butoxycarbonyl-4-ethynyl-oxazolidine (3a) has been prepared in good yield from chiral aminoaldehyde (4) through a two step procedure. Metalation of compound (3a) and subsequent reaction with electrophiles has been investigated leading to the stereoselective synthesis of a new series of substituted alkynes which can be considered us useful precursors of compounds of biological interest