A new and stereospecific synthesis of an inositol analogue: bis-homoinositol

The photooxygenation of trans-8-(acetyloxy)bicyclo[4.2.0]octa-2,4-dien-7-yl acetate afforded the bicyclic endoperoxide. Reduction of the endoperoxide with thiourea followed by acetylation gave the corresponding tetraacetate. The KMnO₄ oxidation of the tetraacetate followed by acetylation gave dihydroxytetraacetate Ammonolysis of tetraacetate afforded the bis-homoinositol, bicyclo[4.2.0]octane-2,3,4,5,7,8-hexol.     

Stereo- and regioselective synthesis of 1,3-diaryl-3-chloro-1-propanols via the reaction of aryl aldehydes with styrene and (E)-β-methylstyrene

Reactions of aryl aldehydes with styrene and (E)-β-methylstyrene in the presence of phenylboron dichloride regioselectively generate 1,3-diaryl-3-chloro-1-propanols and 1,3-diaryl-3-chloro-2-methyl-1-propanols in good to excellent yields with high stereoselectivity.     

High temperature bromination. Part 18: Bromination of benzonorbornadiene derivatives: Polybrominated benzonorbornenes and benzonorbornadienes

The low and high temperature bromination reactions of bromobenzonorbornadiene derivatives were studied and the possible role of a neighboring group in rearrangements was investigated. New polybrominated benzonorbornadiene and benzonorbornene derivatives were synthesized. All compounds were characterized properly using NMR spectroscopy.     

Functionalization of saturated hydrocarbons. High temperature bromination of octahydropentalene. Part 19

The synthesis and thermal bromination of octahydropentalene was studied. The reaction afforded 1a,3a,4b,6b-tetrabromo-1,2,3,4,5,6-hexahydropentalene (14) with remarkable regio- and stereospecificity. The structure of the product was determined by ¹H and ¹³C NMR data and single X-ray structural analysis. The treatment of octahydropentalene with tenfold bromine gave the octabromopentalene derivative. The formation mechanism of the products is discussed.     

Oxidative Difunctionalization of Alkenyl MIDA Boronates: A Versatile Platform for Halogenated and Trifluoromethylated α‐Boryl Ketones

The synthesis of halogenated and trifluoromethylated α‐boryl ketones via a one‐pot oxidative difunctionalization of alkenyl MIDA boronates is reported. These novel densely functionalized organoborons bearing synthetically and functionally valuable carbonyl, halogen/CF₃ and boronate moieties within the same molecule are synthetically challenging for the chemist, but have great synthetic potential, as demonstrated by their applications in a straightforward synthesis of borylated furans. The generality of this reaction was extensively investigated. This reaction is attractive since the starting materials, alkenyl MIDA boronates, are easily accessible.     

Ionic liquids as reagents and solvents in conjunction with microwave heating: rapid synthesis of alkyl halides from alcohols and nitriles from aryl halides

We show that using ionic liquids as reagents in conjunction with microwave heating it is possible to prepare primary alkyl halides from the corresponding alcohols rapidly. Using ionic liquids as solvents in conjunction with microwave heating it is possible to prepare aryl nitriles from the corresponding aryl bromides or iodides. The scope and limitations of using microwave-promotion as a tool in these reactions is discussed.     

Immobilization of HX：[Hmim]X as Halogenating Agent, Recyclable Catalyst and Medium for Conversion of Alcohols to Alkyl Halides

HX is immobilized by reaction of halogen acid with methylimidazole, and the formed ionic liquid [Hmim]X was used as halogenating agent, catalyst as well as medium for conversion of alcohols to alkyl halides. Excellent yields were obtained. The halides produced could be easily separated from the reaction mixture via simple decantation, and the ionic liquid [Hmim]X could be regenerated conveniently by adding equivalent of halogen acids followed by removal of water.     

Reaction of alkenes with hydrogen peroxide and sodium iodide: a nonenzymatic biogenic-like approach to iodohydrins

An efficient protocol to synthesize iodohydrins from alkenes is presented. Reactions were conducted in aqueous media using safe and readily available sodium iodide (the most abundant form of the element), and a highly convenient oxidant such as hydrogen peroxide. Addition of a protic acid triggers a faster and efficient process, a role formally related to that played by haloperoxidase enzymes in naturally occurring transformations. The successful application of these conditions to multigram scale preparations and over natural products derivatives is also discussed.     

Synthesis and structure elucidation of bromination products from dibromohomobenzonorbornadienes: high temperature bromination--part 17

The electrophilic addition of bromine to dibromohomobenzonorbornadiene derivatives at -45 +/- 5 degrees C led to the formation of the rearranged and non-rearranged tetrabromides in a ratio of 6:4. However, high-temperature bromination of the same system in CCl4 at 77 degrees C produced only non-rearranged products. The formation mechanism of the isomers and the role of the substituent on the rearrangement is discussed. The structure elucidation of the isomeric tetrabromides was achieved from NMR spectral data. The agreement between the calculated dihedral angles and the measured coupling constants is especially excellent. The gamma-gauche effect is discussed.     

Porphyrins with exocyclic rings. Part 19: Efficient syntheses of phenanthrolinoporphyrins

5-Nitro-1,10-phenanthrolines react with isocyanoacetate esters in the presence of DBU in THF to give excellent yields of the corresponding phenanthrolinopyrroles. These were condensed with acetoxymethylpyrroles using catalytic quantities of p-toluenesulfonic acid in acetic acid to give dipyrrylmethanes, but these structures proved to be poorly suited for porphyrin synthesis due to the electron-withdrawing nature of the fused phenanthroline unit. However, phenanthrolinopyrrole ethyl esters could be converted to the corresponding α-unsubstituted pyrroles with KOH in ethylene glycol at 180-190 °C, and these condensed with 2 equiv of acetoxymethylpyrroles in refluxing acetic acid-isopropyl alcohol to give tripyrranes. In a one pot procedure, tripyrrane di-tert-butyl esters were treated with TFA at room temperature to cleave the protective groups, diluted with dichloromethane, reacted with pyrrole dialdehydes and oxidized to afford phenanthrolinoporphyrins in 52-83% yield. These conditions also allow the synthesis of porphyrins with additional fused acenaphthylene or phenanthrene rings. Although the UV-vis spectra for these porphyrins are unexceptional, the presence of an external coordination site allows many potential applications to be considered. Porphyrins with two phenanthroline units could not be prepared by the ‘3+1’ strategy. Instead, α-unsubstituted phenanthrolinopyrroles were reacted with a bis(dimethylaminomethyl)pyrrole in refluxing acetic acid to give moderate yields of the corresponding opp-diphenanthrolinoporphyrins. In one case, a triphenanthrolinoporphyrin and trace amounts of an adj-diphenanthrolinoporphyrin were formed as by-products.