Isolable and Readily Handled Halophosphonium Pre-reagents for Hydro- and Deuteriohalogenation.

Although the addition of acid halides across olefins is well-studied, limitations remain with a number of substrate classes that possess leaving groups, polyunsaturation, and acid-sensitive moieties, particularly polyenes prone to cyclization. The process is also challenging when conducted on a small scale, and moreover, methods for the addition of their deuterated counterparts typically require special techniques, especially when control of stoichiometry is required. Herein is described a readily synthesized and handled reagent class which can accomplish the controlled and selective Markovnikov addition of both HCl and HBr across several alkene classes under mild reaction conditions tolerant of diverse functionality.

Alkyldisulfanium Salts: Isolable, Electrophilic Sulfur Reagents Competent for Polyene Cyclizations.

Tools that can effect electrophilic sulfur-promoted cation-π cyclizations are generally lacking, especially using alkylsulfide-based reagents. Herein we report that combining three different 1,2-dithioethers with Cl and SbCl generates isolable alkyldisulfanium salts that can effect such reactions. These new reagents can install -SMe, -SEt, and -SCHCHCF in modest, moderate, or good yield on diverse frameworks, including polyenes that terminate with electron-deficient groups.

Strategies for the Total Synthesis of Diverse Bromo-Chamigrenes.

Several dozen spirocyclic sesquiterpenoids known as the bromo-chamigrenes have been isolated to date. Yet, despite their unique structures, synthetic efforts toward this collection have been modest. Herein, we outline two strategies to generate their skeletons based on (1) a biomimetic bromonium-induced polyene cyclization using BDSB (EtSBr·SbClBr) and (2) a Diels-Alder reaction which ultimately delivered four members of the class.

Asymmetric aza-Morita-Baylis-Hillman reactions of chiral N-phosphonyl imines with acrylates via GAP chemistry/technology.

Chiral N-phosphonyl imines have been proven to be efficient electrophilic acceptors for asymmetric aza-Morita-Baylis-Hillman (aza-MBH) reactions with acrylates under convenient conditions. Thirty examples of β-amino acrylates were generated in high yields (up to 99.4%) and diastereoselectivity (up to >99 : 1 dr) in an atom-economical fashion.

Chiral N-Phosphonyl Imines for an Aza-Morita-Baylis-Hillman Reaction via Group-Assisted Purification (GAP) Chemistry.

Seventeen examples of aza-Morita-Baylis-Hillman (aza-MBH) adducts have been synthesized by reacting chiral N-phosphonyl imines with acrylonitrile in good to excellent yields (up to 96%) and high diastereoselectivity (up to 99:1 dr). The synthesis of these adducts followed the method of group-assisted purification (GAP) chemistry, in which the pure aza-MBH products were readily obtained by washing the crude products with cosolvents of hexane and ethyl acetate.