María T. Lockhart

Selective Synthetic Routes to Sterically Hindered Unsymmetrical Diaryl Ketones via Arylstannanes

Bulky arylstannanes and bulky aroyl chlorides are good reaction partners for the synthesis of two-, three-, and even four-ortho-substituted benzophenones, in good to excellent isolated yields (47-91%). Three simple and direct routes, with differential advantages, are proposed: (i) a catalyst-free protocol, in o-dichlorobenzene (ODCB) at 180 °C; (ii) a room temperature protocol, using AlCl(3) (0.5 equiv), in dichloromethane (DCM); and (iii) a solvent-free, indium-promoted procedure. A radical mechanism is proposed for the indium-mediated reactions.

Efficient Catalyst-Free Bi- And Triaroylation of Aromatic Rings in a Single Step

The exceptional leaving group ability of the trimethylstannyl group in electrophilic aromatic substitutions makes possible the synthesis, in a single step, of bi- and triaroylarenes through the catalyst-free, regioselective reaction of bi- and tristannylarenes with different aroyl halides in o-dichlorobenzene as solvent. Specific di- and triketones are obtained in good to excellent yields (45-83%).

Indium-mediated regioselective synthesis of ketones from arylstannanes under solvent-free ultrasound irradiation.

The solvent-free indium-promoted reaction of alkanoyl chlorides with sterically and electronically diverse arylstannanes is a simple and direct method for the regioselective synthesis of primary, secondary and tertiary alkyl aryl ketones in good to excellent isolated yields (42-84%) under mild and neutral conditions. The protocol is also adequate for the synthesis of aryl vinyl ketones. Reaction times are drastically reduced (from 3-32h to 10-70min) under ultrasonic irradiation. Evidences for the involvement of a homolytic aromatic ipso-substitution mechanism, in which indium metal acts as radical initiator, are presented. It is possible the transference of two aryl groups from tin, thus improving effective mass yield, working with diarylstannanes as starting substrates.

Reactions of haloarenes, haloheteroarenes and dihalobenzenes with triphenylstannyl anions in DMSO and acetonitrile

Abstract We studied different haloarenes, haloheteroarenes and dihalobenzenes with Ph3Sn− ions in DMSO or acetonitrile (CH3CN) as solvents, in the dark or under irradiation to determine whether the halogen metal exchange (HME) reaction or the SRN1 process prevails. With p-chloroanisole the photostimulated reaction is sluggish in DMSO. There is an HME reaction with 2- and 3-chlorothiophene. Bromoarenes (p-bromoanisole, p-dibromobenzene and 1-bromonaphthalene) and p-iodoanisole react with Ph3Sn− ions faster by an HME mechanism than by the SRN1 process. In the photostimulated reaction of 1-chloronaphthalene, 2-chloro and 3-chloropyridines with Ph3Sn− ions in DMSO, the substitution products are obtained in 72, 82 and 93% yields, respectively. With p-dichlorobenzene the di-substitution product is obtained in 90% yield. All these reactions occur by the SRN1 mechanism. Yields improve when the reactions are carried out in DMSO rather than in CH3CN.

Evidence of single electron transfer in the diastereoselective synthesis of β-stannylketones

Abstract The reaction of trimethyl- and triphenylstannylpotassium with mono and disubstituted enones ( 1 – 5 ) in acetonitrile as solvent was studied. In a few seconds and under mild conditions these reactions lead in nearly quantitative yields either to a mixture of diastereomers or to a pure diastereomer of β-stannylketones 6 – 16 . The reactions with triphenylstannylpotassium gave higher yields than trimethylstannylpotassium. The partial or total inhibition of the reactions by addition of a free radical scavenger (galvinoxyl) or a radical–anion scavenger ( p -dinitrobenzene) leads us to believe that these reactions could follow a two-stage reaction mechanism involving an initial electron transfer step. Our results indicate that these reactions are stereoselective but certainly not stereospecific. Full 1 H- and 13 C-NMR data of the new β-stannylketones are given.

Influence of structural features of tri-functionalized aryl phosphates on the outcome of the SRN1 process with stannyl anions: a DFT study

Under irradiation, 1,3-bis(diethoxyphosphoryloxy)-4-chlorobenzene (2), 1,4-bis(diethoxyphosphoryloxy)-3-chlorobenzene (3) and 1,3-bis(diethoxyphosphoryloxy)-5-chlorobenzene (4) react with trimethyltinsodium (1) in liquid ammonia giving entirely different distribution of stannylated products. These differences are explained through theoretical DFT studies. Experimental evidence for the involvement of an SRN1 mechanism was obtained.

Experimental and DFT study on the indium-mediated synthesis of benzophenones via arylstannanes

Experimental results of the solvent-free, indium-promoted reaction of aroyl chlorides with arylstannanes showed a narrow scope; its efficiency depends both on the extent of methylation in the latter and on the nature, number and position of the substituents in the former. With the purpose of explaining experimental results, a theoretical analysis with DFT methods was performed for a set of selected cases.