Halogenation of Heterocycles: II. Six- and Seven-Membered Rings

Application of Phosphonium Salts to the Reactions of Various Kinds of Amides

“…While the reactivity of heteroaromatics has been studied in detail, the study of their basic synthetic reactions like halogenation [8] has remained at a standstill. It is wellknown that heteroaromatic alcohols are chlorinated with phosphorus oxychloride to Scheme give chloroheteroaromatics [9 ± 12].…”

Preparation of 4‐substituted 3‐amino‐2‐chloropyridines, synthesis of a nevirapine analogue

“…Four different chlorination methods [11] have been tried: 1. Gaseous chlorine from a cylinder, 2. sodium hypochlorite solution, 3. chlorine generated in situ by oxidation of concentrated hydrochloric acid with potassium chlorate and 4. chlorine generated in situ by oxidation of hydrochloric acid with hydrogen peroxide.…”

Direct fluorination of coumarin, 6-methyl-coumarin and 7-alkoxy-coumarins

“…Synthetic procedures for the preparation of fluorinated heterocycles include substitution of diazo groups (BalzSchiemann reaction) or chlorine (halogen exchange) by fluorine or cyclisation strategies involving acyclic fluorinated 'building blocks' [1,2,[4][5][6]. However, synthesis of the necessary functionalised precursors can sometimes be very complex and time consuming and, therefore, a more convenient approach to the synthesis of fluorinated heteroaromatic derivatives is, potentially, the selective transformation of carbon-hydrogen bonds to carbonfluorine bonds in reactions involving electrophilic fluorinating agents.…”