Lucio Minuti

High Pressure Diels−Alder Approach to Hydroxy-Substituted 6a-Cyano-tetrahydro-6H-benzo[c]chromen-6-ones: A Route to Δ6-Cis-Cannabidiol

Diels-Alder cycloaddition reactions of 3-cyanocoumarin, hydroxy-substituted 3-cyanocoumarins and mesyl-substituted 3-cyano-coumarins with methyl-1,3-butadienes carried out under high pressure (11 kbar) are reported. Activation by high pressure allows these reactions to proceed satisfactorily under mild conditions to produce 6a-cyano-hydroxy- and 6a-cyano-mesyl-tetrahydro-6H-benzo[c]chromen-6-ones in moderate to excellent yield. The synthesis of cis-1-hydroxy-9-methyl-3-pentyl-6a,7,10,10a-tetrahydro-benzo[c]chromen-6-one as precursor of Delta(6)-3,4-cis-cannabidiol (Delta(6)-cis-CBD) and Delta(8)-cis-tetrahydrocannabinol (Delta(8)-cis-THC) is outlined.

High Pressure Diels-Alder Reactions of 2-Vinyl-3,4-Dihydronaphthalene. Synthesis of Cyclopenta[c]- and Indeno[c]Phenanthrenones.

Abstract A new shorter synthesis of 2-vinyl-3,4-dihydro-naphthalene has been described. The Diels-Alder reactions of this diene with 4-acetoxy-2-cyclopenten-1-one, 3-bromoindan-1-one and inden-1-one under high pressure conditions are reported. A two step synthesis of cyclopenta[c]-and indeno[c]phenanthrenones is discussed. Structure analysis by 1 H and 13 C NMR spectroscopy is presented.

AN EFFICIENT SYNTHETIC APPROACH TO SUBSTITUTED PENTA- AND HEXAHELICENES

A two-step synthetic approach to penta- and hexahelicenes substituted at the terminal aromatic rings has been studied. This approach is based on the Diels–Alder reaction of 5,5′,8,8′-tetramethyl-3,3′,4,4′-tetrahydro-[1,1′]-binaphthalene (2b), 3-vinyl-1,2-dihydronaphthalene (5a), 5,8-dimethyl-3-vinyl-1,2-dihydronaphthalene (5b) and 3-vinyl-1,2-dihydrophenanthrene (15) followed by the aromatization of the cycloadducts. This method is flexible, efficient and of wide application to the synthesis of several benzenoid and nonbenzenoid penta- and hexahelicenes. The racemization energy barriers of helicenes 3, 9, 10, 13, 14, 17 and 18 were computed with the semiempirical quantum method AM1. The computed values show that, when methyl groups are introduced at the inner position of the terminal aromatic rings, the racemization barriers increase markedly. A structure analysis of the reaction products by 1H- and 13C-NMR spectroscopy is also presented.

A new short synthetic approach to cyclopentaphenanthrenones

Abstract The Diels-Alder reactions of 4-acetoxy-2-cyclopenten-1-one and 2-bromo-4-acetoxy-2-cyclopenten-1-one with vinylarenes are discussed. The aromatization of the reaction products opens a new two-step route for the synthesis of cyclopentaphenanthrenones. Structure analysis of reaction products by 1 H and 13 C-NMR spectroscopy is reported.

Determination of phenolic compounds in wines by novel matrix solid-phase dispersion extraction and gas chromatography/mass spectrometry

A novel matrix solid-phase dispersion (MSPD) extraction method was developed to extract simultaneously 23 phenolic compounds from wine samples prior to determination by gas chromatography with mass spectrometric detection in the selected ion monitoring mode. Different parameters of the MSPD technique such as dispersant solid-phase, eluting solvent, and sample ionic strength and pH were optimized. The optimized MSPD procedure requires a small volume of wine (1 mL), commercial silica gel (1.5 g) as dispersant solid-phase and a small volume of ethyl acetate (5 mL) as eluting solvent. Under these conditions, the extraction of the studied compounds was almost complete (mean values of recoveries between 87 and 109%) in a short time (15 min). Moreover, satisfactory standard deviations of repeatability (RSD<9% in most cases), linear regression coefficients (r(2)>0.993) and detection limits (<8 microg/L) confirm the usefulness of the methodology for routine monitoring of the concentration of individual phenolic antioxidants in wines. Application was illustrated by analysis of different wine samples.

[2.2]Paracyclophanes incorporated within poly(3-butylthiophene): synthesis and photoelectrical properties

The synthesis and photoelectrical properties of [2.2]paracyclophanes, containing conjugated acetylenic triple bonds in the linear side-chain, are described. These compounds were incorporated as an electroactive component within a conductive polymer, i.e. poly(3-butylthiophene). The blend showed a photoelectrical response higher than that of the neat polymer. Surprisingly, it was found that the application of an electric bias during the preparation of the blend led to an increase in the photocurrent.

Synthesis of D-erythro-sphinganine through serine-derived α-amino epoxides.

A total synthesis of D-erythro-sphinganine [(2S,3R)-2-aminooctadecane-1,3-diol] starting from commercial N-tert-butyloxycarbonyl-L-serine methyl ester is described. The approach is based on the completely stereoselective preparation of an α-amino epoxide obtained by treating a protected L-serinal derivative with dimethylsulfoxonium methylide. The oxirane synthon is obtained with an anti configuration fitting the (2S,3R) stereochemistry of the 2-amino-1,3-diol polar head of D-erythro-sphinganine. The synthetic procedure afforded the target compound in a 68% overall yield based on the initial amount of the starting L-serine material.

High pressure and thermal Diels–Alder reaction of 2-vinyl-benzo[b]furan and 2-vinyl-benzo[b]thiophene. Synthesis of new condensed heterocycles

Abstract A new preparation of 2-vinyl-benzo[b]furan and 2-vinyl-benzo[b]thiophene is described. Diels–Alder reactions of these dienes with 3-nitro-2-cyclohexen-1-one and 2-inden-1-one was examined under thermal and high pressure conditions. The reaction products have been converted to multi-ring heteroaromatic compounds.

Diels-Alder reactions of arylethenes. Synthesis of some [5]phenacenes and fluorenoanthracenes

Abstract A one-pot high yielding route to 3,4-dihydro-1-(2H)-anthracenone (9) based on high pressure Diels-Alder reaction is described. The synthesis of 3,4-dihydro-1-vinylphenanthrene (1) and 3,4-dihydro-1-vinylanthracene (2) is reported. A new synthetic two-step approach to [5]phenacenes and fluorenoanthracenes has been developed. It is based on the Diels-Alder reaction of arylethenes 1 and 2 with benzyne (13), 1,4-benzoquinone (14), 1,4-naphthoquinone (15) and inden-1-one (17) and on the aromatization of the cycloadducts. Structure analysis of the reaction products by 1H and 13C-NMR spectroscopy is presented.

Deprotection/reprotection of the amino group in α-amino acids and peptides. A one-pot procedure in [Bmim][BF4] ionic liquid

This paper presents an efficient one-pot protocol for the sequential deprotection/reprotection of the α-amino group in α-amino acid and dipeptide methyl esters. [Bmim][BF4] is used as the solvent in the entire process. In particular, the use of the ionic liquid allows for rapid and clean removal of the 4-nitrobenzenesulfonyl (nosyl) group and for facile subsequent tert-butyloxycarbonylation of the free α-amino function under very mild conditions. N-Boc-α-amino acid as well as peptide derivatives are isolated in excellent yields, and do not require any further purification. Absolute configurations of the precursors are totally preserved during the process.