Luis A. Sarandeses

Palladium-catalysed coupling of vinyl triflates with enynes and its application to the synthesis of 1α-25-dihydroxyvitamin D3

Abstract We describe a general approach, based on the palladium-catalysed coupling of enynes with vinyl triflates, for the construction of dienynes related to vitamin D metabolites and analogues. As an application of this method, an efficient convergent synthesis of 1α,25-dihydroxyvitamin D 3 starting from the Inhoffen-Lythgoe diol ( 6a ) and natural carvones has been carried out (11 steps, 28% overall yield from 6a ). This strategy allows labelling of the side chain in the final steps of the synthesis

Palladium-Catalyzed Cross-Coupling Reactions of Organogold(I) Reagents with Organic Electrophiles

The palladium-catalyzed cross-coupling reaction of organogold(I) reagents (alkyl, alkenyl, aryl, and alkynyl) with organic electrophiles, such as aryl and alkenyl halides, aryl triflates, benzyl bromide, and benzoyl chloride is reported. The reaction takes place, under palladium catalysis, at room temperature with short reaction times to give the corresponding cross-coupling products in high yields.

Palladium-catalyzed synthesis of dienynes related to vitamin D from enol triflates

Abstract This note describes a simple synthesis of Lythgoe-type dienynes based on palladium catalyzed coupling of kinetic Grundmanns ketone enol triflate and acetylenic compounds containing the vitamin D A-ring fragment.

Cross-coupling reactions of indium organometallics with 2,5-dihalopyrimidines: synthesis of hyrtinadine A.

The palladium-catalyzed cross-coupling reaction of triorganoindium reagents (R3In) with 5-bromo-2-chloropyrimidine proceeds chemoselectively, in good yields, to give 5-substituted-2-chloropyrimidines or 2,5-disubstituted pyrimidines using 40 or 100 mol % of R3In, respectively. Sequential cross-couplings are also performed, in one pot, using two different R3In. This method was used to achieve the first synthesis of the alkaloid hyrtinadine A. The key step was a two-fold cross-coupling reaction between a tri(3-indolyl)indium reagent and 5-bromo-2-chloropyrimidine.

Synthesis of 3,4-disubstituted maleimides by selective cross-coupling reactions using indium organometallics.

Unsymmetrical 3,4-disubstituted maleimides have been synthesized by palladium-catalyzed cross-coupling reactions of indium organometallics with 3,4-dihalomaleimides. The synthesis was performed by stepwise or sequential one-pot palladium-catalyzed cross-coupling reactions with various triorganoindium reagents. This method was used to prepare a wide variety of alkyl, aryl, heteroaryl, and alkynyl 3,4-disubstituted maleimides in good yields and with high selectivity and atom economy.

Inner–outer ring 1,3-bis(trimethylsilyloxy)-1,3-dienes as useful intermediates in the synthesis of helicenes

Abstract Functionalized benzo[c]phenanthrenes ([4]helicenes) and [5]helicenes were synthesised in five steps from tetrahydronaphthalenone and tetrahydrophenanthrenone compounds using a novel synthetic approach based on a Diels–Alder reaction between inner–outer ring 1,3-bis(trimethylsilyloxy)-1,3-dienes and benzyne or quinones.

Total Synthesis of (+)-Neomarinone

The first total synthesis of (+)-neomarinone has been achieved by following a concise and convergent route using methyl (R)-lactate and (R)-3-methylcyclohexanone as chiral building blocks. Key steps of the synthesis are the stereocontrolled formation of the two quaternary stereocenters by diastereoselective 1,4-conjugate addition and enolate alkylation reactions, and the construction of the furanonaphthoquinone skeleton by regioselective Diels-Alder reaction between a 1,3-bis(trimethylsilyloxy)-1,3-diene and a bromoquinone. The synthesis proves the relative and absolute stereochemistry of natural neomarinone.

A Versatile Enantioselective Synthesis of Barrenazines

A versatile enantioselective total synthesis of barrenazines A and B has been accomplished from 1,4-butanediol. The key steps of the synthesis are a sequential allylboration/ring-closing metathesis for the construction of the tetrahydropyridine ring and the preparation of a functionalized 4-azidopiperidin-5-one through a stereoselective epoxidation and regioselective ring-opening reaction. The C(2)-symmetrical pyrazine skeleton of barrenazines was prepared by dimerization of the azidopiperidinone, and the carbon side chain was completed by copper-catalyzed reactions using Grignard reagents.

Cleavage of 2,3-epoxyalkylhalides by the sonochemical zinc–copper couple

2,3-Epoxyalkylhalides are readily transformed into allylic alcohols when sonicated in the presence of a zinc–copper couple in aqueous ethanol.

Triorganoindium Reagents in Selective Palladium-Catalyzed Cross-Coupling with Iodoimidazoles: Synthesis of Neurodazine

Triorganoindium reagents (R3In, R = aryl, heteroaryl, alkynyl) react selectively under palladium catalysis with N-benzyl-2,4,5-triiodoimidazole to afford the C-2 monocoupling products. The reaction proceeds efficiently for a variety of aryl- and heteroarylindium reagents with the transfer of all three organic groups attached to the metal. The coupling products can be used in a subsequent two-fold cross-coupling to give trisubstituted imidazoles in good yields. This approach was employed to synthesize neurodazine and analogues in good yields.