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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. [ABSTRACT FROM AUTHOR]

The uncatalyzed addition of catecholborane to α-diimines has been examined. Reactions proceed smoothly at room temperature in the absence of a catalyst or additive, providing bis-hydroboration products with 3-coordinate boron centres or mono-hydroboration products with 4-coordinate boron centres, depending on the nature of the diimine reagent. [ABSTRACT FROM AUTHOR]

Abstract We have investigated the addition of a simple phosphinoboronate ester, Ph 2 PBpin (pin = 1,2-O 2 C 2 Me 4), to 2-diphenylphosphinobenzaldehyde (2-Ph 2 PC 6 H 4 C(O)H) and related aldimine derivatives (2-Ph 2 PC 6 H 4 C(NR)H) as a simple and effective strategy for generating unique diphosphine ligands bearing a pendant Lewis-acid Bpin group. These reactions proceed selectively to give one new product where the phosphide fragment has added to the aldehyde (or imine) carbon atom and the electron-deficient boron group has added to the electron-rich heteroatom. Preliminary studies show these new compounds can ligate to Pd(II) and Pt(II) metal centres. These novel metal complexes, as well as the organic soluble [MCl 2 (coe)] 2 (M = Pd, Pt, coe = cis -cyclooctene) compounds, have been shown to be effective precatalysts in the cyclisation of alkynoic acids to give the corresponding exo -dig cyclic lactones. Reactions employing these metal complexes also generated unusual endo -dig cyclic lactones not traditionally observed in these cyclisation reactions. For instance, reactions of 4-pentynoic acid also afforded significant amounts of α-angelica lactone, a biologically-important compound traditionally prepared via the catalytic dehydration and cyclisation of levulinic acid. Graphical abstract The phosphinoboration of 2-diphenylphosphinobenzaldehyde and related aldimines with Ph 2 PBpin is presented as a facile methodology for generating novel diphosphines. Preliminary catalytic alkynoic acid cyclisation studies using the metal complexes are presented. Image 1 Highlights • Phosphinoboration. • Formation of novel diphosphines. • Pd and Pt complexes containing ambiphilic diphosphines. • Active catalysts in the cyclisation of alkynoic acids. • Formation of unusual α-angelica lactone. [ABSTRACT FROM AUTHOR]