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This study reports on the exploration of the phosphinoboration reaction with several thiosemicarbazones (R5R4NC(S)NR3N=CR1R2). Reactions between either Ph2PBpin (pin = 1,2-O2C2Me4) or Ph2PBcat (cat = 1,2-O2C6H4) with thiosemicarbazones containing a terminal primary or secondary amine afforded boron-containing heterocyclic 1,3,4-thiadiazoline products in excellent yield. The addition of Ph2PBpin to thiosemicarbazones containing an NMe2 group in the terminal position generated novel five-membered heterocycles in moderate yield, which included boron, sulfur, and nitrogen atoms. Heterocyclization of the thiosemicarbazones occurs preferentially in the presence of functional groups such as acetyl and pyridyl groups.

This preliminary study reports on the synthesis of two new boron-capsaicin derivatives containing either a short or long chain aliphatic tail group using an iridium catalyzed hydroboration reaction with pinacolborane. The boronate ester groups reside on the terminal position of the tail group and are necessary for the bioactivity of these compounds. Indeed, both compounds showed considerable activity against two Gram-positive bacteria, including Vancomycin-resistant Enterococcus. Vancomycin is considered the last resort medication for the treatment of septicemia, and new antibacterial agents that can treat sepsis are of paramount importance. The more lipophilic boron compound with the longer aliphatic chain also showed antifungal activity against Saccharomyces cerevisiae.

The addition of 4-ethyl-3-thiosemicarbazide to benzaldehyde and boronic acid containing derivatives afforded the corresponding thiosemicarbazones (1–3) or benzodiazaborines (4–6) depending on the position of the boronic acid within the ring. All compounds have been characterized fully including an X-ray diffraction study of the methoxy-containing benzodiazaborine 6. Attempts to coordinate thiosemicarbazones 2 and 3 to palladium(II) acetate were unsuccessful; however, addition of the non-boron-containing derivative 1 to palladium afforded complex 7 whose molecular structure was determined by an X-ray diffraction study. The initial bioactivities of compounds 1–7 were examined against two fungi, Aspergillus niger and Saccharomyces cerevisiae, and two bacteria, Bacillus cereus and Pseudomonas aeruginosa.

Three new iminophosphines containing pinacol-derived boronate esters have been prepared and ligated to dichloridoplatinum(II) fragments. All compounds have been characterized fully, including an X-ray diffraction study carried out for the platinum complex 8, which is derived from 4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)aniline. These three new platinum complexes, along with the non-boron containing control, have been examined for their initial cytotoxic properties against two glioma cell lines using the MTT method.

Ten lipophilic amines were prepared from the reductive amination of vanillin and the corresponding primary amines using sodium borohydride in methanol. All compounds have been obtained elementally pure and an X-ray diffraction study on the 4-n-butylaniline derivative has confirmed the molecular structure. Whilst the overall antibiotic activity of the derivatives was low, some of these compounds, particularly the boronate ester 2-methoxy-4-((2-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenylamino)methyl)phenol (7), showed a promising degree of antimycobacterial activity against Mycobacterium tuberculosis H37Ra, where activity seemed to vary by the position of the boron substitution on the aniline ring.

A small family of organometallic platinum complexes containing a chloride, cis-cyclooctene, and a Schiff base ligand have been prepared and characterized fully. Three aliphatic amines and four aromatic amines were chosen as representative examples. All complexes were stable in air except for 7, derived from the pinacol-protected 4-aminophenylboronate ester 4-H2NC6H4Bpin (pin = 1,2-O2C2Me4), which decomposed via B–C bond cleavage. Both complexes 4 (derived from aniline) and 7 were further characterized by single-crystal X-ray diffraction studies and confirmed the square planar nature of the platinum centre whereby the chloride ligand lies trans to the deprotonated hydroxyl group of the Schiff base ligand. The imine functionality is trans to the organic cyclooctene group. Complex 3, which contained the longest aliphatic chain studied (an octyl group), was the most promising for inducing apoptosis in the malignant MB231 breast cancer cell line. Conversely, complexes 4–6, which contained aromatic groups, were the most active against renal cell carcinoma (RCC) cell lines.

Eight lipophilic 3-hydroxy-4-pyridinones have been prepared from a microwave-mediated reaction along with the corresponding copper(II) complexes. All complexes have been obtained elementally pure and X-ray diffraction studies on two of the copper complexes have confirmed the structure of these compounds. Some of these complexes showed a promising degree of anti-mycobacterial activity against Mycobacterium tuberculosis, where activity seemed to vary by substitution at the pyridinone nitrogen atom.

Addition of 3,5-di-tert-butylcatechol (butcat) to solutions of H3B·SMe2 gave the novel diboron species B2(butcat)3 (2) in moderate to high yields. Compound 2 reacts with Tl(acac) to give butcatB(acac) (4) and Tl(Bbutcat2) (5). Attempts to abstract the chlorides from [(dppb)Rh(µ-Cl)]2 (where dppb = 1,4-bis(diphenylphosphino)buthane) using 5 led to the unusual dimer [(dppb)Rh(µ-Cl)2(µ-Tl)Rh(dppb)][Bbutcat2] (6), which contains an unsymmetrical Rh–Tl–Rh bridge.Key words: arylspiroboronate ester, non-coordinating anion, rhodium, thallium.

Schiff bases, derived from the condensation of salicylaldehydes with 3- and 4-aminophenol, reacted with palladium(II) acetate to give the corresponding bis(N-arylsalicylaldiminato)palladium(II) complexes. These complexes have been found to be active catalysts for the Suzuki–Miyaura cross-coupling of aryl bromides and iodides with aryl boronic acids, using water as a solvent.Key words: cross-coupling, green chemistry, palladium, salicylaldimines, Schiff base, Suzuki–Miyaura.

Three novel rhodium(I) acetylacetonato (acac) complexes bearing phosphinoalkynes (Ph2PC≡C-t-Bu, Ph2PC≡CPPh2, and Ph2PC≡CC≡CPPh2) have been prepared and characterized fully. Addition of B2cat3 (cat = 1,2-O2C6H4) to Rh(acac)(Ph2PC≡C-t-Bu)2 (1a) led to zwitterionic Rh(η6-catBcat)(Ph2PC≡C-t-Bu)2 (2a), the first example of this type of compound to contain monodentate phosphine ligands. All new rhodium complexes have been investigated for their ability to catalyse the hydroboration of vinylarenes.Key words: catalysis, hydroboration, phosphinoalkynes, regioselectivity, rhodium.

The addition of formylphenylboronic acid derivatives to urea and ethyl acetoacetate proceeds in the absence of an additional Lewis acid catalyst to give the corresponding dihydropyrimidinones (Biginelli products) in good yields. Novel boron-containing dihydropyrimidinones have been investigated for their ability to act as anticancer agents against the breast cancer cell line MCF7.Key words: anticancer, Biginelli compounds, boronic acids, breast cancer, dihydropyrimidinones.

Condensation of salicylaldehyde (2-HOC6H4C(O)H) with 2-H2NC6H4Bpin (pin = 1,2-O2C2Me4) afforded the macrocyclic dimer 1 with an OBOBO structural unit. Similar reactivity with substituted salicylaldehyde derivatives gave the corresponding Schiff bases 2–6. Crystals of 1 were triclinic, space group P-1, a = 9.7915(4) Å, b = 10.8569(5) Å, c = 12.8445(6) Å, α = 102.067(1)°, β = 96.011(1)°, γ = 90.458(1)°, Z = 2. All new compounds have been tested for their antifungal activity against Aspergillus niger and Aspergillus flavus.Key words: antifungal, boron, dehydration, heterocycles, Schiff bases.

Condensation of salicylaldehyde (2-HOC6H4C(O)H) with 5-aminosalicylic acid (5-H2NC6H3-2-(OH)-CO2H) afforded the Schiff base 2-HOC6H4C(H)=NC6H3-2-(OH)-5-CO2H (a). Similar reactivity with 5-bromosalicylaldehyde was also observed to give 5-Br-2-HOC6H3C(H)=NC6H3-2-(OH)-5-CO2H (b). Reaction of these salicylaldehydes with Pd(II), Cu(II), and Zn(II) salts gave the corresponding bis(N-arylsalicylaldiminato)metal complexes (M = Pd (1), Cu (2), Zn (3)). The molecular structure of the Schiff base compound a has been confirmed by an X-ray diffraction study. Crystals of a were monoclinic, space group P2(1)/c, a = 7.0164(7) Å, b = 11.0088(11) Å, c = 14.8980(15) Å, β = 102.917(2)°, Z = 4. The molecular structure of a novel zwitterionic conformer of 3a was also characterized by an X-ray diffraction study. Crystals of 4 were monoclinic, space group P2(1)/c, a = 9.5284(5) Å, b = 19.5335(11) Å, c = 8.6508(5) Å, β = 90.596(1)°, Z = 4. All new compounds have been tested for their antifungal activity against Aspergillus niger and Aspergillus flavus. Key words: 5-aminosalicylic acid (5-ASA), antifungal, copper, palladium, salicylaldimines, Schiff base, zinc.

We have prepared the aryl sulfonamides 4,4′-R-C6H4SO2NHC6H4CH=CH2 (R = CH3, 1a; NO2, 1b) by addition of 2 equiv. of 4-vinylaniline to the corresponding sulfonyl chlorides. The disulfonamides 4,4,4′-(R-C6H4SO2)2NC6H4CH=CH2 (R = CH3, 2a; NO2, 2b) were also prepared using 4-vinylaniline and 2 equiv. of the sulfonyl chlorides in the presence of DMAP. Although hydroborations of sulfanilamide derivatives 1 suffered from competing hydrogenation reactions, judicious choice of the transition metal catalyst gave selective formation of either the primary or secondary boronate esters in hydroborations of 2a.Key words: boronate esters, catalysed hydroborations, sulfanilamides, vinylaniline.

Condensation of 2-pyridinecarboxaldehydes with 2-, 3-, and 4-H2NC6H4Bpin (pin = 1,2-O2C2Me4) gave the corresponding boron-containing pyridinecarboxaldimines (N–NBpin). Addition of these ligands to [PtCl2(coe)]2 (coe = cis-cyclooctene) gave complexes of the type cis-PtCl2(N–NBpin) in moderate yields. The platinum complexes have been examined for their potential cytotoxicities against OV2008 (human ovarian carcinoma) and the analogous cisplatin-resistant cell line C13. Key words: boronate esters, pyridinecarboxaldimines, cytotoxicity, platinum, boron.

Oxidative cyclization of 2-aminothiophenol, 2-aminophenol, and 1,2-phenylenediamine with 2-thiophenecarboxaldehyde affords the corresponding 2-thiophen-2-ylbenzothiazole, -benzoxazole, and -benzimidazole compounds. Addition of these ligands (L) to [PtCl2(coe)]2 (coe = cis-cyclooctene) gives complexes of the type trans-PtCl2L(coe) in moderate yields. Crystals of the benzothiazole derivative (1) were monoclinic, space group P2(1)/c, a = 11.561(4) Å, b = 15.335(15) Å, c = 11.769(4) Å, β = 105.182(5)°, Z = 4.Key words: platinum, imine, benzothiazole, benzoxazole, benzimidazole.

Five platinum pyridin-2-ylcarboxaldimine complexes of the type cis-[PtCl2(2-C5H4NCH=NR)] (R = CH2CH2OH (1); R = N(CH2CH2)2O (2); R = C6H5 (3); R = 1-C10H7 (4); R = (CH2)8CH=CH(CH2)7CH3 (5)) were prepared and their in vitro reactivity towards a 20-base pair (single- and double-stranded) DNA determined using nuclease digest studies and RP-HPLC. Variation of the imine functionality allowed for the design of compounds with different physical and chemical properties. Complexes 1 and 3 showed binding to both single- and double-stranded DNA comparable to that of cisplatin (cis-[PtCl2(NH3)2]). Crystals of 1 were monoclinic, space group P2(1)/n, a = 9.6612 (15), b = 12.9678 (19), c = 9.7004(13) Å, β = 117.73(3)°, Z = 4.Key words: platinum, pyridin-2-ylcarboxaldimines, DNA binding studies.

Condensation of α-diketones (2,3-butanedione, benzil, and acenaphthenequinone) with 3-H2NC6H4Bpin (pin = 1,2-O2C2Me4) gave the corresponding boron-containing α-diimines. The addition of these ligands to [MCl2(coe)]2 (coe = cis-cyclooctene, M = Pd or Pt) gave complexes of the type cis-MCl2(α-diimine) in moderate to high yields. The platinum complexes have been examined for their ability to bind to DNA using enzyme digest studies. These complexes were found to bind to single-stranded DNA as well as, or better than, the non-boron containing controls, and showed binding similar to that of cisplatin (cis-PtCl2(NH3)2).Key words: boronate esters, diazabutadienes, DNA-binding, platinum.

Condensation of 2-aminophenol with boronate ester derivatives of benzaldehyde afforded the corresponding boron-containing Schiff bases, 2-HOC6H4N=C(H)C6H4R (1a: R = 2-Bpin; 1b: R = 3-Bpin; 1c: R = 4-Bpin; pin = 1,2-O2C2Me4). Crystals of 1b were triclinic, space group P[Formula: see text], a = 11.9420(6), b = 13.0871(7), and c = 13.2720(7) Å, α = 70.983(1), β = 67.793(1), and γ = 78.380(1)°, Z = 2. Reaction of 2-aminophenol with 2-HC(O)C6H4B(OH)2 in EtOH, however, gave a macrocyclic dimer 2 with a OBOBO structural unit. The molecular structure of this dimer has been confirmed by an X-ray diffraction study. Crystals of 2 were monoclinic, space group P21/c, a = 10.0447(8), b = 21.0894(15), and c = 12.6214(9) Å, β = 105.301(2)°, Z = 4. Further reaction of these Schiff bases with manganese triacetate in toluene afforded 2-arylbenzoxazoles 3a–c via an oxidative cyclization pathway. The molecular structure of the 4-Bpin derivative (3c) was characterized by an X-ray diffraction study. Crystals of 3c were monoclinic, space group P21/n, a = 6.5392(3), b = 16.3330(8), and c = 16.1942(8) Å, β = 97.9620(10)°, Z = 4.Key words: boron heterocycles, Schiff bases, arylbenzoxazoles.

The in situ rhodium-catalyzed addition of catecholborane (HBcat, cat = 1,2-O2C6H4) and pinacolborane (HBpin, pin = 1,2-O2C2Me4) to allylamine, allylimine, 2- and 4-vinylpyridines, and a thienyl imine has been examined using multinuclear NMR spectroscopy. Although reactions of allylamine (H2NCH2CH=CH2) and HBcat gave complex product distributions arising from competing dehydrogenative borylation pathways, addition of HBpin to allylamine using a rhodium catalyst afforded only products arising from hydroboration (RN(Bpin)CH2CH2CH2Bpin, where R = H, Bpin) and hydrogenation (RN(Bpin)CH2CH2CH3). Hydroboration of allylimines (RHC=NCH2CH=CH2, R = Ar) with HBcat occurs initially at the more reactive imine functionality to give unsaturated borylamines (RCH2N(Bcat)CH2CH=CH2). Further reaction with HBcat gives varying amounts of hydroboration products RCH2N(Bcat)CH2CH2CH2Bcat and RCH2N(Bcat)CH2CH(Bcat)CH3 as well as the diboration product RCH2N(Bcat)CH2CH2CH(Bcat)2, depending on the choice of catalyst. Reactions with related unsaturated pyridine derivatives are complicated by extensive degradation, which can be avoided by coordination of the pyridine nitrogen to a Lewis acid. The first examples of metal-catalyzed hydroboration of imines using HBpin are also reported.Key words: catalysis, hydroboration, boronate esters, dehydrogenative borylation, allylimines.

Addition of 3-H2NC6H4Bpin (pin = 1,2-O2C2Me4) to a series of aldehydes and 4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)acetophenone afforded the corresponding benzylideneamines in moderate to high yields. Hydroboration of these imines with catecholborane (HBcat, cat = 1,2-O2C6H4) at room temperature gives, upon aqueous workup, the corresponding borylamines. An X-ray diffraction study was carried out on imine 1h derived from 9-anthraldehyde and 3-H2NC6H4Bpin. Crystals of1h were triclinic, a = 9.6793(4) Å, b = 10.7397(4) Å, c = 11.5353(4) Å, α = 105.1890(10)o, β = 97.3030(10)o, γ = 102.1480(10)o, Z = 2 with space group P[Formula: see text] and crystals of N-[3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl]-4-methoxybenzylamine 2c were orthorhombic, a = 8.6612(4) Å, b = 10.3794(4) Å, c = 20.6033(9) Å, Z = 4 with space group P212121. Amines have been tested for their antifungal properties against Aspergillus niger and Aspergillus flavus.Key words: benzylamines, boronate esters, aminoboron, hydroboration, antifungal.

We have prepared a number of complexes of the type cis-MoO2L2 where L represents a hydroxypyronato or hydroxypyridinonato ligand. Both the maltol (3-hydroxy-2-methyl-4-pyrone, Hma) and kojic acid (5-hydroxy-2-hydroxymethyl-4-pyrone, Hka) complexes, cis-MoO2(ma)2 (1) and cis-MoO2(ka)2 (2), have been characterized by X-ray diffraction studies. The pyrone ligands are bound to molybdenum in a cis bidentate fashion via the deprotonated hydroxyl groups and the ketone moieties. Crystals of 1 are orthorhombic, a = 12.107 (1), b = 8.6169 (8), c = 16.472 (1) Å, Z = 4, space group Pca21, and those of 2 are monoclinic, a = 8.4591 (5), b = 16.3453 (10), c = 10.2954 (7) Å, β = 103.0320 (10)°, Z = 4, space group P21/c. Hydroxypyridinone molybdenum complexes have been prepared for both maltol and kojic acid derivatives with the substituents Me, n-Pr, CH2Ph, Ph at the ring nitrogen. Crystals of the 3-hydroxy-2-methyl-1-phenyl-4-pyridinone (Hppp) derivative, MoO2(ppp)2 (9), are monoclinic, a = 10.9476 (6), b = 13.5353 (9), c = 17.4877 (10) Å, β = 93.465 (4)°, Z = 4, space group P21/n. Initial investigations into the effects molybdenum compounds have on diabetic hearts are presented. Both Na2MoO4 (used as a control) and 1 were effective in lowering blood glucose and free fatty acid levels. Diabetic rats treated with molybdate showed significant improvements in postischemic cardiac function.Key words: molybdenum, hydroxypyrones, hydroxypyridinones, heart function.

Reactions of 3-NH2C6H4B(OH)2 (1, APBA) with [MCl4]2- (M = Pd, Pt) give the boronic acid-containing complexes, MCl2(APBA)2 (M = Pd, 2; M = Pt, 3). Addition of 1 to [PdCl2(COE)]2 (COE = η2-C8H14) ultimately led to PdCl2(APBA)2 (2). The pinacol derivative PdCl2(APBpin)2 (5, pin = O2C2Me4) was characterized by an X-ray diffraction study. Crystals of 5 were monoclinic, a = 13.836(5), b = 14.937(5), c = 11.287(5) Å, β = 99.042(9)°, Z = 2, with space group P21/c. Monoalkene complexes PtCl2(COE)(APBA) (8) and PtCl2(COE)(APBpin) (9) were generated from the addition of APBA and APBpin, respectively, to [PtCl2(COE)]2. Reactions of 2-NMe2CH2C6H4B(OH)2 (10) with palladium complex [PdCl2(COE)]2 proceed via selective B—C bond cleavage to give the cyclopalladated dimer [PdCl(2-NMe2CH2C6H4)]2 as the major amine-containing product. Likewise, reactions with borinic esters H2NCH2CH2OBR2 (R = Bu, 14; R = Ph, 15) give products derived from cleavage of the B—O bond. The unique palladium complex PdCl2[3-NC5H4B(OH)2]2 (19) was prepared by addition of (3-NC5H4BEt2)4 (18) to [PdCl2(COE)]2 in wet methylene chloride, where adventitious water was used to convert the organoborane product into the corresponding boronic acid moiety.Key words: aminoboronic acids, platinum, palladium, cyclomηllation.