Palladium(II)-assisted conversion of a 2-alkenyl sulfone into a 3-acetoxy(or chloro)-1-alkenyl sulfone

2-alkenyl p-tolyl sulfone was converted into the corresponding 3-acetoxy-1-alkenyl p-tolyl sulfone via a π-allyl palladium complex which underwent regiospecific attack of a nucleophile, acetate ion, and the reaction conditions for predominant formation of 3-chloro-1-alkenyl p-tolyl sulfone are also described.     

Reaction of magnesium alkylidene carbenoids with lithium alpha-sulfonyl carbanions: a novel synthesis of tri- and tetra-substituted allenes from 1-chlorovinyl p-tolyl sulfoxides and sulfones

Treatment of 1-chlorovinyl p-tolyl sulfoxides, which were synthesized from ketones and chloromethyl p-tolyl sulfoxide, with ethylmagnesium chloride or isopropylmagnesium chloride at below -78 degrees C gave magnesium alkylidene carbenoids in about 90% yields. The reaction of the generated carbenoids with lithium alpha-sulfonyl carbanions was found to afford tri- and tetra-substituted allenes. Both cyclic ketones and acyclic ketones were useful in this procedure. However, the 1-chlorovinyl p-tolyl sulfoxides derived from aldehydes gave only rearranged products, acetylenes, under the reaction conditions. The magnesium alkylidene carbenoid derived from an optically active 1-chlorovinyl p-tolyl sulfoxide was treated with lithium alpha-carbanion of 1-naphthyl phenyl sulfone; however, the obtained allene was found to be racemic. The mechanism of this reaction is also discussed.     

25,27-dithiasapphyrin and pyrrole-inverted isomer of 21,23-dithiaporphyrin from condensation of pyrrole and 2,5-bis(p-tolylhydroxymethyl)thiophene

[see structure]. A novel aromatic isomer of 5,10,15,20-tetra(p-tolyl)-21,23-dithiaporphyrin (S2TTP) with an inverted pyrrole ring, 5,10,15,20-tetra(p-tolyl)-2-aza-21-carba-22,24-dithiaporphyrin (S2CTTP), and 5,10,15,20-tetra(p-tolyl)-25,27-dithiasapphyrin (25,27-S2TTSH), have been obtained by a condensation of 2,5-bis((p-tolyl)hydroxymethyl)thiophene and pyrrole. A conformational equilibrium, unique in a sapphyrin class, between two S(27)-thiophene-flipped and planar structures of neutral 25,27-S2TTSH was detected by 1H NMR.     

Aryl vinyl sulfones as thiol protective group

Phenyl vinyl sulfone and p-tolyl isobutenyl sulfone are convenient reagents for protecting SH groups via the Michaël adduct. Protection and deprotection can be achieved in high yields under mild basic conditions, in protic or aprotic solvents.     

A new and efficient method for the selective olefination of aldehydes with ethyl diazoacetate catalyzed by an iron(II) porphyrin complex.

Olefination of aromatic and aliphatic aldehydes with ethyl diazoacetate was achieved in excellent yields with triphenylphosphine and catalytic amounts of iron(II) meso-tetra(p-tolyl)porphyrin. The reaction conditions are mild and the process is efficient and highly selective (>90%) for the synthesis of the trans-olefin isomer. Results of mechanistic studies are discussed.     

The practical procedure for a preparation of 1-chloroalkyl p-tolyl sulfoxides in high optically active form: A very short synthesis of optically active disparlure

A chlorination of optically active alkyl p-tolyl sulfoxides with N-chlorosuccinimide in dichloromethane in the presence of potassium carbonate afforded optically active 1-chloroalkyl p-tolyl sulfoxides in 87–94% ee (88–94% chemical yields). The optically active chloroalkyl sulfoxide was applied to a synthesis of optically active (+)-disparlure.     

Combined ruthenium(II) and lipase catalysis for efficient dynamic kinetic resolution of secondary alcohols. Insight into the racemization mechanism

Pentaphenylcyclopentadienyl ruthenium complexes (3) are excellent catalysts for the racemization of secondary alcohols at ambient temperature. The combination of this process with enzymatic resolution of the alcohols results in a highly efficient synthesis of enantiomerically pure acetates at room temperature with short reaction times for most substrates. This new reaction was applied to a wide range of functionalized alcohols including heteroaromatic alcohols, and for many of the latter, enantiopure acetates were efficiently prepared for the first time via dynamic kinetic resolution (DKR). Different substituted cyclopentadienyl ruthenium complexes were prepared and studied as catalysts for racemization of alcohols. Pentaaryl-substituted cyclopentadienyl complexes were found to be highly efficient catalysts for the racemization. Substitution of one of the aryl groups by an alkyl group considerably slows down the racemization process. A study of the racemization of (S)-1-phenylethanol catalyzed by ruthenium hydride eta(5)-Ph(5)CpRu(CO)(2)H (8) indicates that the racemization takes place within the coordination sphere of the ruthenium catalyst. This conclusion was supported by the lack of ketone exchange in the racemization of (S)-1-phenylethanol performed in the presence of p-tolyl methyl ketone (1 equiv), which gave <1% of 1-(p-tolyl)ethanol. The structures of ruthenium chloride and iodide complexes 3a and 3c and of ruthenium hydride complex 8 were confirmed by X-ray analysis.     

An effective and mild electrocatalytic procedure for the removal of 1,3-dithiane protecting groups

The 1,3-dithiane protecting group can effectively be removed by indirect electrochemical oxidation under extremely mild conditions, if catalytic amounts of tris(p-tolyl)amine are used as homogeneous electron transfer agents.     

Anion-dependent self-assembly of silver(I) and diaminotriazines to coordination polymers: non-covalent bonds and role interchange between silver and hydrogen bonds

New coordination polymers have been obtained by the self-assembly of silver salts AgX (X = BF 4, PF 6, CF 3SO 3) and 2,4-diamino-6-R-1,3,5-triazines L (R = phenyl and p-tolyl) of formulas AgLX ( 1- 6). A complex of different stoichiometry, [Ag 3L 2(H 2O)(acetone) 2](BF 4) 3, 7 (R = phenyl), has also been synthesized. The three-dimensional structures of five compounds have been determined by X-ray diffraction studies. For the AgLX complexes, when X = BF 4 and R = phenyl or p-tolyl, chiral chains with alternating Ag and L are formed. The chains are cross-linked by the counteranions in a three-dimensional fashion through hydrogen bonds and weak Ag...F interactions giving rise to a structure with solvent-filled channels. Different and more compact structures have been found when the counteranion is CF 3SO 3 (OTf). When R = phenyl, sheets are formed which consist of [Ag 2(OTf) 2L 2] units with double triflate bridges and which contain columns of pi-pi stacked arenes. Hydrogen bonds connect the sheets. When AgOTf is used and R is p-tolyl, a different and unusual ladderlike structure is obtained in which the rungs are double asymmetric bridges consisting of the triflate groups bonded to Ag in kappa (2) O,mu 2- O and kappa (1) O,mu 2- O fashion. The ladders are parallel to each other and are mutually linked by N-H...N hydrogen bonds to give a 3D architecture. A very similar ladderlike structure has been found for 7 but with a water molecule and a BF 4 (-) group acting as bridges. The role played by the hydrogen bonds in complex 6 to form the 3-D structure is played in 7 by [Ag(acetone) 2] fragments. The noncovalent interactions play an important role in the different solid-state 3D structures. The behavior of the new derivatives in solution has also been analyzed. A new species has been detected at low temperatures, and this exhibits restricted rotation of the phenyl ring.     

Three-dimensional structure determination of N-(p-Tolyl)-dodecylsulfonamide from powder diffraction data and validation of structure using solid-state NMR spectroscopy

The three-dimensional structure, conformation, and packing of molecules in the solid state are crucial components used in the optimization of many technologically useful materials properties. Single-crystal X-ray diffraction is the traditional and most effective method of determining 3-D structures in the solid state. Obtaining single crystals that are sufficiently large and free of imperfections is often laborious, time-consuming, and, occasionally, impossible. The feasibility of an integrated approach to the determination and verification of a complete three-dimensional structure for a medium-sized organic molecule without using single crystals is demonstrated for the case of an organic stabilizer compound N-(p-tolyl)-dodecylsulfonamide. The approach uses a combination of powder XRD data, several computational packages involving Monte Carlo simulations and ab initio quantum mechanical calculations, and experimental solid-state NMR chemical shifts. Structure elucidation of N-(p-tolyl)-dodecylsulfonamide revealed that the Bravais lattice is monoclinic, with cell dimensions of a = 38.773 A, b = 5.507 A, c = 9.509 A, and beta = 86.35 degrees, and a space group of P21/c.     

Aldehyde and ketone syntheses using methylthiomethyl p-tolyl sulfone

Methylthiomethyl p-tolyl sulfone (1) was conveniently alkylated to give mono- and dialkylated products (2 and 4). Reaction conditions for the trasformation of 2 and 4 into aldehydes (3) and ketones (5), respectively, were exploited.     

A new efficient route to 2-substituted azulenes based on sulfonyl group directed lithiation

Directed lithiation of p-tolyl 1-azulenyl sulfone (1) at the 2-position of the azulenyl group was achieved by using lithium 2,2,6,6-tetramethylpiperidide (LTMP). The azulenyllithium thus generated could be efficiently trapped with various electrophiles to form 2-substituted derivatives 2 in moderate to good yields. p-Tolyl 2-trimethylsilyl-1-azulenyl sulfone (2a) was transformed into cyclic sulfone derivative 3a through the directed lithiation in the p-tolyl group and subsequent intramolecular ring closure at the 8-position. 2-(Phenylsulfanyl)-1-azulenyl p-tolyl sulfone (2b) suffered from desulfonylation to form 2-phenylsulfanylazulene (4). The Suzuki coupling reaction of 2-iodo-1-azulenyl p-tolyl sulfone (2d) with arylboronic acids followed by desulfonylation efficiently gave 2-arylazulenes 10.     

Novel synthesis of 2-arylbenzothiazoles mediated by ceric ammonium nitrate (CAN): a rebuttal

[reaction: see text] The reported synthesis of 2-arylbenzothiazoles mediated by ceric ammonium nitrate (CAN) is irreproducible; the only products formed in this reaction are bis-(p-tolyl) disulfide and p-tolyl p-toluenethiosulfonate.     

Using enzyme inhibition as a high throughput method to measure the enantiomeric excess of a chiral sulfoxide

[reaction: see text] The enantiomeric excess of methyl p-tolyl sulfoxide can be determined in a high throughput format by measuring its ability to inhibit the alcohol dehydrogenase catalyzed oxidation of ethanol. The two enantiomers of the sulfoxide have very different inhibition constants for the enzyme. Thus, the initial rate of ethanol oxidation in the presence of the sulfoxide is correlated with the sulfoxide enantiomeric excess.     

Reactivity of silole within a core-modified porphyrin environment: synthesis of 21-silaphlorin and its conversion to carbacorrole

Condensation of 1,1-dimethyl-3,4-diphenyl-2,5-bis(p-tolylhydroxymethyl)silole with pyrrole and p-tolylaldehyde did not form the expected 21,21-dimethyl-2,3-diphenyl-5,10,15,20-tetra(p-tolyl)-21-silaporphyrin, but rather its reduced derivative, 21-silaphlorin, which contains a tetrahedrally hybridised C5 carbon atom. Attempts to trap 21-silaporphyrin resulted in the serendipitous discovery of a unique transformation of 21-silaphlorin into a non-aromatic isomer of 2,3-diphenyl-5,10,15,21-tetra(p-tolyl)-carbacorrole (iso-carbacorrole). This novel carbaporphyrinoid contains a cyclopentadiene ring embedded in a tripyrrolic framework. This transformation of 21-silaphlorin to iso-carbacorrole, carried out under oxidative conditions, involves extrusion of dimethylsilylene accompanied by migration of the C(meso)-(p-tolyl) unit to create a cyclopentadiene ring directly linked to the adjacent pyrrole through a tetrahedral carbon atom. Insertion of silver or copper ions into iso-carbacorrole gave two structurally related organometallic complexes of "true" carbacorrole in which the metal(III) ions are bound by three pyrrolic nitrogen atoms and a tetrahedrally hybridised C21 atom of the cyclopentadiene moiety. In the presence of oxygen, the silver(III) carbacorrole undergoes internal oxidation to 21-oxacorrole. The structure of silver(III) carbacorrole was determined by X-ray crystallography. The C21 atom was found to have a tetrahedral geometry. The Ag-C(sp(3)) (2.046(5) A) bond length is similar to that in silver(III) carbaporphyrinoids in which a trigonal carbon atom coordinates to the metal ion. Density functional theory was applied to model the molecular and electronic structure of 21-silaphlorin and feasible isomers of carbacorrole. The total energies (kcal mol(-1) vs. iso-carbacorrole), calculated at the B3LYP/6-31G(**)//B3LYP/6-31G(*) level for carbacorrole, iso-carbacorrole, vacataporphyrin and cyclobutadienephlorin, demonstrate the energetic preference for iso-carbacorrole.     

Stereoselective addition of alpha-sulfinyl carbanions to N-p-tolylsulfinylketimines: synthesis of optically pure 1,2,2'-trialkyl-2-aminoethanols

The reactions of lithium carbanions derived from both enantiomers of methyl (1) and ethyl p-tolyl sulfoxide (2) with (S)-N-arylsulfinylketimines 3 and 4 took place in a highly stereoselective manner and good isolated yields. The configuration of the carbon bonded to nitrogen relies exclusively on the N-sulfinylimine configuration. When ethyl p-tolyl sulfoxide (2) is use as nucleophile, two chiral centers are created simultaneously, where the configuration of the carbon bonded to the sulfur is mainly controlled by 2. The asymmetric induction increases with the temperature, being total at room temperature in the case of the matched pair of reactants. A non-oxidative Pummerer reaction on the obtained aminosulfoxides allows a straightforward synthesis of optically pure 1,2-ethanolamines with one or two chiral centers, including amino alcohols with a bulky quaternary carbon bonded to the amine group.     

Titanium and niobium imido complexes stabilized by heteroscorpionate ligands

The reaction of [Ti(NR)Cl(2)(py)(3)](R = (t)Bu, p-tolyl, 2,6-C(6)H(3)(i)Pr(2)) with [{Li(bdmpza)(H(2)O)}(4)][bdmpza = bis(3,5-dimethylpyrazol-1-yl)acetate] and [{Li(bdmpzdta)(H(2)O)}(4)][bdmpzdta = bis(3,5-dimethylpyrazol-1-yl)dithioacetate] affords the corresponding complexes [Ti(NR)Cl(kappa(3)-bdmpzx)(py)](x = a, R = (t)Bu 1, p-tolyl 2, 2,6-C(6)H(3)(i)Pr(2) 3; x = dta, R =(t)Bu 4, p-tolyl , 2,6-C(6)H(3)(i)Pr(2) 6), which are the first examples of imido Group 4 complexes stabilized by heteroscorpionate ligands. The solid-state X-ray crystal structure of 1 has been determined. The titanium centre is six-coordinate with three fac-sites occupied by the heteroscorpionate ligand and the remainder of the coordination sphere being completed by chloride, imido and pyridine ligands. The complexes are 1-6 fluxional at room temperature. The pyridine ortho- and meta-proton resonances show evidence of dynamic behaviour for this ligand and variable-temperature NMR studies were carried out in order to study their dynamic behaviour in solution. The complexes [Nb(NR)Cl(3)(py)(2)](R = (t)Bu, p-tolyl, 2,6-C(6)H(3)(i)Pr(2)) reacted with [{Li(bdmpza)(H(2)O)}(4)] and (Hbdmpze)[bdmpze = 2,2-bis(3,5-dimethylpyrazol-1-yl)ethoxide], the latter with prior addition of (n)BuLi, to give the complexes [Nb(NR)Cl(2)(kappa(3)-bdmpzx)](x = a, R =(t)Bu 7, p-tolyl 8, 2,6-C(6)H(3)(i)Pr(2) 9; x = e, R = (t)Bu 10, p-tolyl 11, 2,6-C(6)H(3)(i)Pr(2)) 12 and these are the first examples of imido Group 5 complexes with heteroscorpionate ligands. The structures of these complexes have been determined by spectroscopic methods.     

One-electron versus two-electron mechanisms in the oxidative addition reactions of chloroalkanes to amido-bridged rhodium complexes

The compound syn-[{Rh(mu-NH{p-tolyl})(CNtBu)(2)}(2)] (1) oxidatively adds C--Cl bonds of alkyl chlorides (RCl) and dichloromethane to each metal centre to give the cationic complexes syn-[{Rh(mu-NH{p-tolyl})(eta(1)-R)(CNtBu)(2)}(2)(mu-Cl)]Cl and anti-[{Rh(mu-NH{p-tolyl})Cl(CNtBu)(2)}(2)(mu-CH(2))]. Reaction of 1 with the chiral alkyl chloride (-)-(S)-ClCH(Me)CO(2)Me (R*Cl) gave [{Rh(mu-NH{p-tolyl})(eta(1)-R*)(CNtBu)(2)}(2)(mu-Cl)]Cl ([3]Cl) as an equimolecular mixture of the meso form (R,S)-[3]Cl-C(s) and one enantiomer of the chiral form [3]Cl-C(2). This reaction, which takes place in two steps, was modeled step-by-step by reacting the mixed-ligand complex syn-[(cod)Rh(mu-NH{p-tolyl})(2)Rh(CNtBu)(2)] (4) with R*Cl, as a replica of the first step, to give [(cod)Rh(mu-NH{p-tolyl})(2)RhCl(eta(1)-R*)(CNtBu)(2)] (5) with racemization of the chiral carbon. Further treatment of 5 with CNtBu to give the intermediate [(CNtBu)(2)Rh(mu-NH{p-tolyl})(2)RhCl(eta(1)-R*)(CNtBu)(2)], followed by reaction with R*Cl reproduced the regioselectivity of the second step to give (R,S)-[3]Cl-C(s) and [3]Cl-C(2) in a 1:1 molar ratio. Support for an S(N)2 type of reaction with inversion of the configuration in the second step was obtained from a similar sequence of reactions of 4 with ClCH(2)CO(2)Me first, then with CNtBu, and finally with R*Cl to give [(CNtBu)(2)(eta(1)-CH(2)R)Rh(mu-NH{p-tolyl})(2)(mu-Cl)Rh(eta(1)-R*)(CNtBu)(2)]Cl (R = CO(2)Me, [7]Cl) as a single enantiomer with the R configuration at the chiral carbon. The reactions of 1 with (+)-(S)-XCH(2)CH(CH(3))CH(2)CH(3) (X = Br, I) gave the related complexes [{Rh(mu-NH{p-tolyl})(eta(1)-CH(2)CH(CH(3))CH(2)CH(3))(CNtBu)(2)}(2)(mu-X)]X, probably by following an S(N)2 profile in both steps.     

Development of new synthetic methods with aryl 1-chlorovinyl sulfoxides

Aryl 1-chlorovinyl sulfoxides were easily synthesized from ketones and aldehydes with aryl chloromethyl sulfoxide in three-steps with high overall yields. Low-temperature treatment of the aryl 1-chlorovinyl sulfoxides with alkyllithium or a Grignard reagent gave alkylidene carbenoids via a sulfoxide-metal exchange reaction. From the alkylidene carbenoids, acetylenic compounds, tetra-substituted olefins, and allenes were synthesized. Enolization of alpha-chloro alpha-sulfinyl ketones, which were synthesized from methyl esters and chloromethyl phenyl sulfoxide, is another method for the generation of aryl 1-chloroalkyl sulfoxides. Treatment of 1-chlorovinyl phenyl sulfoxides so generated with t-BuLi followed by some nucleophiles having an acidic hydrogen gave one-carbon elongated carboxylic acids and their derivatives. Conjugate addition of some carbanions with 1-chlorovinyl p-tolyl sulfoxides was found to have taken place. For example, reaction of 1-chlorovinyl p-tolyl sulfoxides with cyanomethyllithium gave high yields of cyclic enaminonitriles. Acidic treatment of the enaminonitriles afforded good yields of 4,4-disubstituted 2-cyclopentenones. By using unsymmetrical ketones and optically pure chloromethyl p-tolyl sulfoxide, this procedure suggests a good method for an asymmetric synthesis of optically pure 4,4-disubstituted 2-cyclopentenones. This method achieved an asymmetric total synthesis of (+)-alpha-cuparenone starting from methyl 4-methylphenyl ketone and (R)-(-)-chloromethyl p-tolyl sulfoxide. A novel synthesis of 2,4,4-trisubstituted 2-cyclopentenones is also successful using cyanomethyllithium and its homologues. Conjugate addition of the lithium enolate of tert-butyl acetate and its homologues gave high yields of the adduct, 3,3-disubstituted esters. Synthesis of various kinds of carboxylic acids and their derivatives and lactones was realized from the adducts.     

Sulfoxide carbon-sulfur bond activation

The alkynylsulfoxide, TMSCCSO(p-tolyl) (TMS = trimethylsilyl, tolyl = C6H4Me), undergoes reaction with (eta5-C5H5)Co(PPh3)2 at room temperature to give the cobaltosulfoxide complex, (C5H5)Co(PPh3)(eta1-CCTMS)[eta1-(S)-SO(p-tolyl)], which was characterized by X-ray crystallography. Exposure of this cobaltosulfoxide complex to oxygen gas leads to the formation of the corresponding metallosulfone complex, (C5H5)Co(PPh3)(eta1-CCTMS)[eta1-(S)-SO2(p-tolyl)], which was characterized by X-ray crystallography. Alternatively, in solution at room temperature, the metallosulfoxide is converted to a 1:4 mixture of the equatorial-equatorial and equatorial-axial bridging cobalt-thiolato dimers, {(C5H5)Co[mu-S(p-tolyl)]}2, respectively. The equatorial-equatorial isomer was characterized by X-ray crystallography.