Solvent/Oxidant-Switchable Synthesis of Multisubstituted Quinazolines and Benzimidazoles via Metal-Free Selective Oxidative Annulation of Arylamidines
摘要:
A fast and simple divergent synthesis of multisubstituted quinazolines and benzimidazoles was developed from readily available amidines, via iodine(III)-promoted oxidative C(sp(3))-C(sp(2)) and C(sp(2))-N bond formation in nonpolar and polar solvents, respectively. Further selective synthesis of quinazolines in polar solvent was realized by TEMPO-catalyzed sp(3)C-H/sp(2)C-H direct coupling of the amidine with K2S2O8 as the oxidant. No metal, base, or other additives were needed.
Compounds of the formula ##STR1## wherein each of R, R.sub.1 and R.sub.2 is independently H, alkyl, alkenyl, alkoxy, halo, hydroxy, trifluoromethyl, amino, alkylamino, cyano and nitro; R.sub.3 is carbalkoxy, carboxamide alkanoyl, trifluoromethyl and cyano; and Ar is heteroaryl or ##STR2## wherein R.sub.4 and R.sub.5 have the same meaning as each of R, R.sub.1 and R.sub.2 ; and acid addition salts thereof have cardiotonic and hypertensive activity.
BF<sub>3</sub>-Promoted Ring Expansion of Iminylphosphiranes and Acylphosphiranes for Divergent Access to 1,2-Azaphospholidines and 1,2-Dihydrophosphetes
作者:Mingyue Cui、Yang Xu、Rongqiang Tian、Zheng Duan
DOI:10.1021/acs.orglett.3c04347
日期:2024.3.8
Ringexpansion of strained smallrings provides an efficient method for the synthesis of various high-value carbocycles and heterocycles. Here we report BF3·Et2O as both an activating reagent and fluorine source, enabling ringexpansion of phosphirane and P–F bond formation. Treatment of 1-iminylphosphirane complexes with BF3·Et2O resulted in 1,2-azaphospholidines, while the reaction of 1-acylphosphirane
应变小环的扩环为合成各种高价值碳环和杂环提供了一种有效的方法。在这里,我们报告BF 3 ·Et 2 O既作为活化剂又作为氟源,使得磷杂环扩环并形成P-F键。用BF 3 ·Et 2 O处理1-亚氨基正膦配合物得到1,2-氮杂磷烷,而1-酰基正膦配合物与BF 3 ·Et 2 O反应得到1,2-二氢磷酸酯。通过 N 和 O 原子对中间体鏻阳离子的亲核性来调整反应路径。
Asymmetric aza-Claisen rearrangement of allyl imidates catalyzed by homochiral cationic palladium(II) complexes
作者:Yasuhiro Uozumi、Kazuhiko Kato、Tamio Hayashi
DOI:10.1016/s0957-4166(98)00059-7
日期:1998.3
The asymmetric aza-Claisen rearrangement of (E)-3-alkyl-2-propenyl N-[4-trifluoromethyl)phenyl]benzimidates was catalyzed by a homochiral cationic palladium(II) complex generated from PdCl2(S)-2-(2-diphenylphosphino)phenyl-4-benzyloxazoline} and silver tetrafluoroborate (Pd:silver=1:1) to give (S)-N-(1-alkyl-2-propenyl)-N-[4-(trifluoromethyl)phenyl]benzamide of up to 81% ee. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.
First Enantioselective Catalyst for the Rearrangement of Allylic Imidates to Allylic Amides
作者:Michael Calter、T. Keith Hollis、Larry E. Overman、Joseph Ziller、G. Greg Zipp
DOI:10.1021/jo962090p
日期:1997.3.1
A series of Pd(II) complexes containing chiral diamine ligands were investigated as asymmetric catalysts for the rearrangement of allylic imidates to allyl amides. The best catalysts were cations obtained by dechlorination of dichloro[(S)-2-(isoindolinylmethyl)-N-methylpyrrolidine]palladium-(II) (II) (17) with silver salts in CH2Cl2. Catalyst 18 was studied thoroughly and shown by H-1 NMR and X-ray crystallography analysis to be a C-1 symmetric dimer (Figure 1). A series of related catalysts 22-27 having various counterions and anionic ligands were also prepared and studied as asymmetric catalysts for the rearrangement of allylic N-(4-trifluorophenyl)benzimidate 29 to allylic benzamide 30 (eq 4). Rearrangement of 29 in CH2Cl2 (48 h at 40 degrees C) in the presence of 5 mol % of 18 affords (-)-30 in 69% yield and 55% ee. Enantioselection is increased to 60% when an isomerically pure sample of 18 is employed. Chemical correlation of allylic benzamide 30 with (R)-norvaline established that (-)-30 has the R absolute configuration (Scheme 3). A cyclization-induced rearrangement mechanism (Scheme 1) requires that in the major pathway the imidate nitrogen attacks the re face of the olefin with Pd coordinated to the si face. These studies constitute the first report of asymmetric catalysis of the rearrangement of allylic imidates to allylic amides. However, significant hurdles remain to be overcome before the enantioselective rearrangement of allylic imidates becomes a practical route to enantioenriched nitrogen compounds.