Prosím počkejte chvíli...
Nepřihlášený uživatel
Nacházíte se: VŠCHT PrahaFCHTÚOCH  → Vědecké skupiny → Cibulka → Výzkum
iduzel: 15100
idvazba: 18433
šablona: stranka
čas: 22.9.2017 01:09:08
verze: 3813
uzivatel:
remoteAPIs:
branch: trunk
Obnovit | RAW

Výzkum

 Photocatalytic esterification under Mitsunobu reaction conditions mediated by flavin and visible light

DOI:10.1039/C6OB02770A

Graphical abstract: Photocatalytic esterification under Mitsunobu reaction conditions mediated by flavin and visible light

Abstract

The usefulness of flavin-based aerial photooxidation in esterification under Mitsunobu reaction conditions was demonstrated, providing aerial dialkyl azodicarboxylate recycling/generation from the corresponding dialkyl hydrazine dicarboxylate. Simultaneously, activation of triphenylphosphine (Ph3P) by photoinduced electron transfer from flavin allows azo-reagent-free esterification. An optimized system with 3-methylriboflavin tetraacetate (10%), oxygen (terminal oxidant), visible light (450 nm), Ph3P, and dialkyl hydrazine dicarboxylate (10%) has been shown to provide efficient and stereoselective coupling of various alcohols and acids to esters with retention of configuration.

Visible Light [2+2] Photocycloaddition Mediated by Flavin Derivative Immobilized on Mesoporous Silica

DOI:10.1002/cctc.201601654

Link to full-size graphical abstractAbstract

7,8-Dimethoxy-3-methylalloxazine was immobilized on mesoporous silica (MCM-41) to provide a heterogenized flavin photocatalyst. Thus, the prepared heterogeneous catalyst 2 was found to sensitize the visible light [2+2] cycloaddition of various types of dienes to produce corresponding cyclobutanes in high yields and diastereoselectivities. Use of 2 enables procedures which are advantageous owing to simple operation and workup, no additives required, and minimum waste generation.

 

 

Flavin-Mediated Visible-Light [2+2] Photocycloaddition of Nitrogen- and Sulfur-Containing Dienes

DOI:10.1002/ejoc.201601377

Abstract

The [2+2] photocycloaddition mediated by 1-butyl-3-methyl-7,8-dimethoxyalloxazine (1) has been found to be an effective tool for cyclising ω-phenyl- and ω,ω′-diphenyl-4-aza-1,6-heptadienes, in which the nitrogen atom is protected by acylation or quaternisation, towards the synthesis of a variety of phenyl- and diphenyl-3-azabicyclo[3.2.0]heptanes and their corresponding quaternary salts. Thia derivatives, with the sulfur atom in the form of a sulfone group, underwent an analogous cyclisation. Advantageously, visible light (400 nm) was used for the cycloadditions in the presence of 1, in contrast to the previously described procedures affording azabicyclo[3.2.0]heptanes by using UV irradiation. Practical applications are demonstrated through the synthesis of bicyclic quaternary ammonium salts, 6-phenyl-azabicyclo[3.2.0]heptanes known to exhibit biological activity or chiral spiro ammonium salts. Flavin 1 was also found to promote the efficient EZ isomerisation of electron-rich cinnamyl derivatives to produce mixtures enriched with the Z isomer (with Z/E ratios of up to 77:23).

Link to full-size graphical abstract

Aktualizováno: 25.5.2017 14:30, Autor: Martina Kovandová


A BUDOVA A Ústav organické chemie se nachází ve 2. patře budovy A na straně ke Studentské ulici, sekretariát ústavu – místnost A278
B BUDOVA B V 1. patře se nachází Laboratoř forenzní analýzy biologicky aktivních látek
C BUDOVA C
VŠCHT Praha
Technická 5
166 28 Praha 6 – Dejvice
IČO: 60461373
DIČ: CZ60461373

Copyright VŠCHT Praha 2014
Za informace odpovídá Ústav organické chemie, technický správce Výpočetní centrum

zobrazit plnou verzi