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3-Phenylimidazo[1,2- a]pyridines were synthesized through the perfluorohexyl iodide mediated coupling of 2-aminopyridines and phenylacetylenes. In situ iodination of the terminal alkyne by perfluorohexyl iodide reverses the polarity by generating a transient electrophilic iodoalkyne, and this alters the regioselectivity of the phenyl group. The reaction then proceeds by tandem electrophilic alkynylation and cyclization to form the fused-ring product. The protocol affords the 3-phenyl isomer with full regioselectivity and is complementary to reported methodologies for the synthesis of the 2-phenyl isomer starting from the same substrates. [ABSTRACT FROM AUTHOR]

A straightforward synthesis of 5-phenylthiazolamines by coupling thiourea with phenylacetones, phenylacetophenones, and β-tetralone has been developed. Thiourea acts as a substrate and an α-bromination shuttle by transferring a Br atom from CBrCl3 to the α-carbon of the carbonyl moiety. A series of steps are then triggered to reach the final product. Isolated yields from 80 to 95 % were obtained. Key features of this protocol include its minimal use of reagents (i.e., substrates, CBrCl3, and CsHCO3), its short reaction times under mild conditions (at 80 °C for 2-3 h), and its ease of scale up to prepare gram quantities of product. [ABSTRACT FROM AUTHOR]

Abstract: KF/γ-alumina is an effective catalyst for the aldol condensation of citral with acetone. Even at a relatively low acetone/citral ratio of 1–10, the selectivity to pseudoionones was high, ranging between 82% and 97%. X-ray diffraction shows the presence of KF and K3AlF6 crystallographic phases on the supported catalyst. At KF loadings of 3–6.75mmolg−1, a pretreatment of the catalyst by heating to 450°C was necessary to obtain an active catalyst. However, samples with KF loadings of 8.5mmolg−1 and higher were active even without pretreatment, facilitating handling and use of the catalysts. The development of (111) planes revealed by in situ XRD during the thermal activation process correlates with the activity for aldol condensation. [Copyright &y& Elsevier]

Abstract: The addition of nickel to Zr-beta gave a useful bifunctional catalyst that combines a high rate of cyclization of (±)-citronellal to isopulegols over zirconium sites and subsequent hydrogenation to menthols. The diastereoselectivity to the desired (±)-menthol was 90%. A loading of 4 wt% is optimal; lower loadings led to a low rate of hydrogenation, whereas a higher nickel loading appears to block the zirconium Lewis acid sites essential for the cyclization of citronellal. A mixture of Zr-beta and Ni/MCM-41 also formed an effective bifunctional catalyst system where the selectivity toward menthols remained high even with nickel loadings up to 15 wt%. The yield of (±)-menthol over the dual-catalyst system was 86–89% with of byproducts, citronellol and 3,7-dimethyloctanol. Besides nickel, bifunctional Rh/Zr-beta catalysts also formed menthols with selectivity , although the diastereoselectivity to (±)-menthol was lower (85%). In comparison, a 2% Pd/Zr-beta catalyst exhibited lower activity and selectivity to menthols, forming substantial amounts of 3,7-dimethyloctanal. [Copyright &y& Elsevier]

Abstract: The catalytic cyclisation of citronellal was studied over Zr-zeolite beta, micro/mesoporous Al-MSU-SFAU, and microporous HY catalysts. All samples showed good activity in the cyclisation of citronellal to form isopulegols with >97% selectivity. A high diastereoselectivity for (±)-isopulegol of ∼93% was observed over Zr-zeolite beta, whereas Al-MSU-SFAU and HY showed a lower selectivity of ∼65%. Zr-zeolite beta was synthesised in a range of Si/Zr of 75–200 with the use of fluoride and zeolite beta seeds. Zeolite beta with Al and Ti substitution was less active and selective than Zr-zeolite beta. The rate of reaction strongly depended on the type of solvent used, but the reaction could also be carried out without any solvent. A hydroxylated surface is important for good activity. This is consistent with the proposed mechanism, where both Lewis and Brønsted acid sites are essential for the reaction. [Copyright &y& Elsevier]