María-Jesús Villa

Stereochemical control in the synthesis of tetrahydrofurans by cyclisation of diols with phenylthio migration

Abstract Cyclisation of diols with PhS migration leads to tetrahydrofurans by inversion at both the migration origin and terminus. Cyclisation to a secondary migration terminus is controlled by stereochemical factors.

Tandem carbophilic addition-N-acyliminium ion cyclization for the synthesis of functionalized pyrrolo[2,1-a]isoquinolones: Key intermediates for the preparation of Erythrina-type alkaloids

Abstract Sequential carbophilic addition of organolithium reagents- N -acyliminium ion cyclization of N -phenenethylsuccinimide 3 yields pyrrolo[2,1-a]isoquinolones 1 in high yields, with the possibility of varying the substituent at C-10b by changing the organolithium. Application of this methodology to the cis -norbor-5-en-2,3-dicarboximide 7 using a functionalized organolithium reagent, the 3-(2-trimethylsilyl-1,3-dithian-2-yl)propyllithium 11 , followed by desilylation and subsequent retro-Diels-Alder reaction affords the α,β-unsaturated pyrroloisoquinolone 9b , immediate precursor of Erythrina -type alkaloids.

Parham-type cyclization and nucleophilic addition - N-acyliminium ion cyclization sequences for the construction of the isoquinoline nucleus

Abstract Efficient methodologies based on the nucleophilic addition-N-acyliminium ion cyclization and the Parham-type cyclization sequences of N-phenethylimides 1 and 2 are reported for the synthesis of a variety of heterocyclic systems: benzo[a]quinolizidones and their 2-oxa analogs, isoindoloisoquinolones, dibenzo[a,h]quinolizidones, thiazolo-, oxazolo-, and imidazolo [4,3-a]isoquinolones.

Synthesis of 5-arylpyrrolo[2,1-a]isoquinolin-3(2H)-ones from N-phenethylsuccinimides and organolithium reagents

Abstract The 5-aryl-8,9-dialkoxypyrrolo[2,1-a]isoquinolin-3(2H)-ones 1 and 2, which can be considered as 3-arylisoquinoline derivatives, can be efficiently prepared by reaction of the N-1,2-bis(3,4-dimethoxyphenyl)ethylsuccinimides 3 with organolithium reagents, the key steps being a carbonphilic addition-cyclization via N-acyliminium ions and Parham-type cyclization, respectively. In both cases, no competition with the cyclization to the five membered nitrogen ring is observed, which is consistent with the fact that when reacted with organolithium reagents N-benzylsuccinimides 4 did not cyclize to the corresponding pyrroloisoindolones 5 and 6.

An improved method for the generation of imines and enamides. Application to the synthesis of 3-arylisoquinoline derivatives

Abstract The one-pot preparation of hindered 1,2-diarylethylamines 3 and 4 and ethylenenamides 5 is achieved via sodium cyanoborohydride reduction and acylation of the deoxybenzoin imines 2 , respectively. A new methodology for the synthesis of 3-arylisoquinolinium salts by the Bischler-Napieralski reaction of 1,2-diarylethylenenamides and their transformation into 12-methyl substituted benzo[c]phenanthridines has been developed.

[1,4] Phenylthio shifts of 2,4,4-trisphenylthiobutanols

Abstract The title compounds ( 1 ) undergo a [1,4]-PhS shift to give an E,Z mixture of vinyl sulphides ( 2 ) with thionyl chloride but only the Z isomer if toluene- p -sulphonic acid is used. The reaction occurs only if another PhS group is present β to the hydroxyl. The starting materials ( 1 ) were available via Michael addition of dithioacetal nucleophiles ( 3 ) to methyl crotonate followed by α-sulphenylation.

Tandem conjugate addition of silylcuprate and benzenesulfenyl chloride to unsaturated esters: stereoselective preparation of anti-3-dimethylphenylsilyl-2-phenylthio aldehydes

Conjugate addition of dimethylphenylsilylcuprate is successful even to a 2,3-disubstituted acrylate ester and when followed by α-sulfenylation of the trapped silyl enol ether intermediate, reduction and re-oxidation gives, for example, (2SR, 3RS)-(anti)-2, 5-dimethyl-3-dimethylphenylsilyl-2-phenylthiohexanal as a single diastereoisomer.

Stereochemical control in the synthesis of tetrahydrofurans by cyclisation of diols with [1,2]-phenylsulfanyl migration

Acid catalysed rearrangement of a series of 4-PhS-1,3-diols with toluene-p-sulfonic acid in benzene gives stereospecifically substituted 3-PhS-tetrahydrofurans in excellent yield via a [1,2]-SPh shift. We comment on the structural variation at both the migration origin and terminus on the outcome of the title reaction and define its limits.

[1,4] Phenylthio migrations in the rearrangement of 2,4,4-tris(phenylthio)butanols

2,4,4-Tris(phenylthio)butanols rearranged by a [1,4]-PhS shift to give an E,Z mixture of vinyl sulfides with thionyl chloride but only the Z isomer with toluene-p-sulfonic acid. The [1,4]-PhS shift occurred only if another PhS group was present β to the hydroxyl group. The mechanism and scope of the reaction and the preparation of 2,4,4-tris(phenylthio)butanols via Michael addition of dithioacetal nucleophiles to methyl crotonate followed by α-sulfenylation is reported.