RESUMEN
A light induced, transition-metal-free C-C coupling reaction of 2-chlorobenzazoles with aliphatic carbamates, alcohols, and ethers is presented. Inexpensive reagents, namely sodium acetate, benzophenone, water, and acetonitrile, are employed in a simple reaction protocol using a cheap and widely available 25 W energy saving UV-A lamp at ambient temperature.
RESUMEN
Surprisingly, the photocatalytic activation of ethers by H-abstraction and addition of the generated radicals to iminium ions formed in situ from aldehydes and anilines predominantly yielded the products of methoxy activation for dimethoxymethane and 1,2-dimethoxyethane. Various anilines and aromatic as well as aliphatic aldehydes are suitable reaction partners for this three-component photoreaction (Porta-type process) which also provides a simple access to 1,2-aminoalcohols.
RESUMEN
The first total synthesis of the dimeric berberine alkaloid ilicifoline (ilicifolineâ B) is reported. Its carbon skeleton is constructed from ferulic acid, veratrole, and methanol. The synthesis reported herein employs starting materials solely derived from wood. The natural product is thus constructed entirely from renewable resources. The same strategy is applied to a formal total synthesis of morphinan alkaloids. The use of wood-derived building blocks (xylochemicals) instead of the conventional petrochemicals represents a sustainable alternative to classical synthetic approaches.
Asunto(s)
Alcaloides de Berberina/síntesis química , Productos Biológicos/síntesis química , Madera/química , Alcaloides de Berberina/química , Productos Biológicos/química , Estructura MolecularRESUMEN
A facile one-pot synthesis of protoberberines from readily accessible 1,2,3,4-tetrahydroisoquinoline-1-carbonitriles and 1,2-bis(bromomethyl)arenes is described. The reaction cascade comprises four consecutive transformations, all of which can be effected under a single set of conditions. Ten protoberberines, including the alkaloids pseudopalmatine and pseudoepiberberine, were prepared in yields up to 86% according to this strategy. No chromatographic purification of the products is required, and the route is devoid of any protecting group manipulations.
Asunto(s)
Alcaloides/química , Alcaloides/síntesis química , Compuestos de Amonio/química , Alcaloides de Berberina/química , Alcaloides de Berberina/síntesis química , Nitrilos/química , Tetrahidroisoquinolinas/química , Estructura MolecularRESUMEN
The benzoxazol-2-yl- substituent was found to act as a removable activating and directing group in the Ir-catalyzed alkylation of C(sp(3))-H bonds adjacent to nitrogen in secondary amines. It can be easily introduced by oxidative coupling or by an SNAr reaction, and it can be removed by hydroxide or by hydride reduction. For 1,2,3,4-tetrahydroisoquinolines, activation exclusively takes place in the 3-position. A variety of activated as well as unactivated terminal olefins are suitable reaction partners.
RESUMEN
The Stevens rearrangement of nitrile-stabilized ammonium ylides in conjunction with the reductive removal of the nitrile function permits the facile construction of α-branched amines from α-aminonitriles. We employed this reaction sequence for the preparation of (±)-laudanosine, (±)-laudanidine and (±)-armepavine, (±)-7-methoxycryptopleurine, and (±)-xylopinine from two closely related and readily accessible bicyclic α-aminonitriles. The final products were obtained in high to almost quantitative yields (71-98%) from the quaternary ammonium salts obtained by N-alkylation of these starting materials.
Asunto(s)
Bencilisoquinolinas/síntesis química , Alcaloides de Berberina/síntesis química , Isoquinolinas/síntesis química , Nitrilos/química , Compuestos de Amonio Cuaternario/síntesis química , Quinolizinas/síntesis química , Bencilisoquinolinas/química , Alcaloides de Berberina/química , Isoquinolinas/química , Estructura Molecular , Compuestos de Amonio Cuaternario/química , Quinolizinas/química , EstereoisomerismoRESUMEN
The Stevens rearrangement of a nitrile-stabilized ammonium ylide is the key step of a very short and practical synthesis of the phenanthroindolizine alkaloid (±)-tylophorine. The method requires only five linear steps and is devoid of any protecting group manipulations.