Visible-light-promoted Regio-and Stereoselective Oxyalkenylation Of Phosphinyl Allenes

Allenes are attractive molecules possessing two cumulative carbon-carbon double bonds,which show different reactivity from other conjugated systems.Since Haszeldine reported the first addition of a trifluoromethyl radical to an allene in 1954,the reactions of allenes with highly reactive radical species have become topics of allene chemistry.However,radicalbased polyfunctionalization of allenes is still scarce,because the tolerance of the functional group and the resulting E/Z isomer mixture limit the potential application value of the product.Therefore,how to construct a target molecular skeleton with high regio-and stereoselectivity is still a challenge in organic synthesis methodologies.Conjugated dienes can be widely found in natural products and drug molecules.Organophosphorus compounds also play an important role in the fields of life,medicine and pesticides.The synthesis of phosphorus-containing conjugated diene has great significance and application prospects.Based on this,we disclose a highly regio-and stereoselective oxyalkenylation of phosphinyl allenes.The specific research content is introduced from the following two aspects:1?The synthesis of tri-substitued phosphinyl allenesA variety of substituted alkynyl alcohols were prepared via trimethylsilylacetylene with different ketones.The synthesis of phosphinyl allenes by employing alkynol and chlorodiphenylphosphine under the base.The method provides good functional group tolerance and high yield.14 tri-substitued phosphinyl allenes were synthesized,of which 9 were unreported compounds.2?Visible-light-promoted regio-and stereoselective oxyalkenylation of phosphinyl allenesThe difunctionalization of allenes have been established as powerful and stepeconomical approaches to enrich molecular complexity by introducing two groups in one step.A highly regio-and stereoselective oxyalkenylation of tri-substituted phosphinyl allenes is revealed in this paper.This protocol,merging visible light photoredox and palladium catalysis,provides a straightforward access to conjugated tertiary allylic alcohol derivatives with broad functional group tolerance in good to excellent yields.Mechanistic studies reveal that,although two possible pathways exist in the transformation,radical oxyalkenylation promoted by visible light photoredox takes over the major pathway.31 oxyalkenylation products were successfully synthesized,all of which were unreported compounds.The compounds were characterized by nuclear magnetic resonance spectroscopy(1H NMR,13C NMR,31P NMR),mass spectrometry(HRMS),infrared spectroscopy,melting point,single crystal diffraction(X-ray).Synthetic application of the products could be extended with catalytic amount of AlCl3 to building stereoselective[3]Dendralenes,which providing a new method for the synthesis of[3]Dendralenes.