Iodine-promoted sequential Michael and oxidative dehydrogenation processes: synthesis of trisubstituted methanes containing a coumarin and a chromone ring
摘要:
An iodine-promoted convenient and environmentally friendly sequential method for the synthesis of trisubstituted methanes bearing a coumarin and a chromone ring is described. The remarkable features of this approach include avoidance of metals, working under air, employment of readily available starting materials, good functional group tolerance and simple operation. (C) 2015 Elsevier Ltd. All rights reserved.
Topochemical photodimerization of (E)-3-benzylidene-4-chromanone derivatives from β-type structures directed by halogen groups
摘要:
Halogen substituent plays an important role in the crystalline packing of aromatic compounds. The [2+2] photocycloaddition of (E)-3-benzylidene-4-chromanones in the crystalline state was investigated, and halogen substitution has been adopted to organize molecules with proper arrangement for photodimerization. Not halogen bonds, but the electron-withdrawing property of halogen atoms can enhance the face-to-face pi-pi interactions. Therefore, F, Cl or Br substitution at the para position of phenyl gave rise to almost the same beta-structures with face-to-face pi-stacking. Only resulted beta-structures can undergo photodimerization, which gave the syn-HH (syn-head-to-head) products with high regio-/stereoselectivity. (C) 2011 Elsevier Ltd. All rights reserved.
Facile synthesis of spiro chromanone-tetrahydrothiophenes with three contiguous stereocenters via sulfa-Michael/aldol cascade reactions
作者:Ya-Jian Hu、Xiao-Bing Wang、Su-Yi Li、Sai-Sai Xie、Kelvin D.G. Wang、Ling-Yi Kong
DOI:10.1016/j.tetlet.2014.11.026
日期:2015.1
A novel sulfa-Michael/aldol cascade reaction of (E)-3-arylidenechroman-4-ones with 1,4-dithiane-2,5-diol has been developed. This method provides a new practical and facile approach to 4′-hydroxy-2′-aryl-4′,5′-dihydro-2′H-spiro[chroman-3,3′-thiophen]-4-ones with three contiguous stereocenters in high yields. The transformation is atom-economic with good to excellent diastereoselectivities.
Asymmetric Three-Component Cyclizations toward Structurally Spiro Pyrrolidines via Bifunctional Phosphonium Salt Catalysis
作者:Lixiang Zhu、Xiaoyu Ren、Zhongxiu Liao、Jianke Pan、Chunhui Jiang、Tianli Wang
DOI:10.1021/acs.orglett.9b03282
日期:2019.11.1
Asymmetric multicomponent reactions toward optically pure compounds are highly attractive but extremely challenging. Presented herein is a highly diastereo- and enantioselectivethree-component cyclization of exocyclic alkenes with aldehydes and amino esters, which was enabled by bifunctional phosphonium salt catalysts. A wide range of multiply substituted spiro pyrrolidine derivatives were prepared
Iodine-promoted sequential Michael and oxidative dehydrogenation processes: synthesis of trisubstituted methanes containing a coumarin and a chromone ring
作者:Ya-Jian Hu、Neng Jiang、Sai-Sai Xie、Su-Yi Li、Jin-Shuai Lan、Ling-Yi Kong、Xiao-Bing Wang
DOI:10.1016/j.tet.2015.08.056
日期:2015.10
An iodine-promoted convenient and environmentally friendly sequential method for the synthesis of trisubstituted methanes bearing a coumarin and a chromone ring is described. The remarkable features of this approach include avoidance of metals, working under air, employment of readily available starting materials, good functional group tolerance and simple operation. (C) 2015 Elsevier Ltd. All rights reserved.
Topochemical photodimerization of (E)-3-benzylidene-4-chromanone derivatives from β-type structures directed by halogen groups
作者:Xue-Ming Cheng、Zhi-Tang Huang、Qi-Yu Zheng
DOI:10.1016/j.tet.2011.09.087
日期:2011.11
Halogen substituent plays an important role in the crystalline packing of aromatic compounds. The [2+2] photocycloaddition of (E)-3-benzylidene-4-chromanones in the crystalline state was investigated, and halogen substitution has been adopted to organize molecules with proper arrangement for photodimerization. Not halogen bonds, but the electron-withdrawing property of halogen atoms can enhance the face-to-face pi-pi interactions. Therefore, F, Cl or Br substitution at the para position of phenyl gave rise to almost the same beta-structures with face-to-face pi-stacking. Only resulted beta-structures can undergo photodimerization, which gave the syn-HH (syn-head-to-head) products with high regio-/stereoselectivity. (C) 2011 Elsevier Ltd. All rights reserved.