Relative and absolute stereocontrol in intramolecular nitrone cycloadditions to the cyclohexene ring
摘要:
The intramolecular reactivity of a nitrone derived from 2-(cyclohexen-3-yloxy)benzaldehyde has been investigated. By using (R)-alpha-phenylethylamine as chiral auxiliary, enantiomerically pure (9-amino-substituted) 1,2,3,4,4a,9a-hexahydro-9H-xanthen-1-ols were produced in satisfactory way. Copyright (C) 1996 Published by Elsevier Science Ltd
Tetrahydrobenzochromene Synthesis Enabled by a Deconjugative Alkylation/Tsuji–Saegusa–Ito Oxidation on Knoevenagel Adducts
作者:Primali V. Navaratne、Alexander J. Grenning
DOI:10.1021/acs.orglett.8b01857
日期:2018.8.3
A modular and practical route to versatile cyano-1,3-dienes by a sequence involving deconjugative alkylation and “Tsuji–Saegusa–Ito oxidation” is reported. In this letter, the versatility of the products is also explored, including a route to benzochromene scaffolds common to many natural products.
RAPID ASSEMBLY OF POLYCYCLIC STRUCTURES VIA SIGMATROPIC REARRANGEMENT OF S-PROPARGYL XANTHATES
作者:Samir Z. Zard、Ryan M. Harrington、David Wright
DOI:10.3987/com-12-s(n)98
日期:——
based on chemical transformations that cannot be rationalized otherwise. These transformations hinge for most part on exploiting the allylic anion character of this species (only two canonical structures 3a and 3b are drawn for clarity). OR" S S R [3,3]-! O"R S S C R" O R" O S S S S R' R R' R R' R R' 1 2 3a 3b Scheme 1. An unusual betaine derived from S-propargyl xanthates ––––––––––––––––––––––––––––
在氯苯中加热后,炔丙基黄原酸酯产生相应的 4,5-双(亚烷基)-1,3-二硫杂环戊烷-2-酮,它们在分子内 Diels-Alder 环加成中被未活化的烯烃捕获,产生有趣的多环结构。多年来,我们发现源自黄原酸盐的自由基为合成各种分子结构提供了丰富多样的化学物质。在我们的研究过程中,我们发现了 S-炔丙基黄原酸盐 1 的一种不寻常的非自由基化学性质。我们观察到,在加热时,S-炔丙基黄原酸盐经历 [3,3]-σ 重排,得到相应的丙二烯 2,其与结构 3 的新型甜菜碱平衡存在(方案 1)。平衡几乎完全有利于丙二烯 2,甜菜碱 3 存在的证据是间接的,并且基于化学转化,否则无法合理化。这些转变在很大程度上取决于利用该物种的烯丙基阴离子特性(为清楚起见,仅绘制了两个规范结构 3a 和 3b)。OR" SSR [3,3]-! O"RSSC R" O R" OSSSS R' R R' R R' R R' 1
An efficient synthesis of some thiopyranopyrazole-heterocycles via domino reaction in a Brønsted acidic ionic liquid
作者:Narsidas J. Parmar、Bhagyashri D. Parmar、Tushar R. Sutariya、Rajni Kant、Vivek K. Gupta
DOI:10.1016/j.tetlet.2014.09.026
日期:2014.10
thiopyranopyrazole-heterocycles when it was assembled with a variety of O-alkenylated/alkynylated salicylaldehydes and naphthaldehydes in Brønsted acidic ionic liquid, [Hmim]HSO4, via domino/Knoevenagel–hetero-Diels–Alder (DKHDA) reaction. The reaction is highly stereoselective and the work-up procedure required no chromatography of products in many cases.
One-pot synthesis, biological evaluation, and docking study of new chromeno-annulated thiopyrano[2,3-c]pyrazoles
作者:Bhagyashri D. Parmar、Tushar R. Sutariya、Gaurangkumar C. Brahmbhatt、Narsidas J. Parmar、Rajni Kant、Vivek K. Gupta、Prashant R. Murumkar、Mayank Kumar Sharma、Mange Ram Yadav
DOI:10.1007/s11030-016-9665-z
日期:2016.8
AbstractA one-potsynthesis of new chromeno-annulated thiopyrano[2,3-c]pyrazoles has been achieved through a domino-Knoevenagel–hetero-Diels–Alder reaction after combining various pyrazol-5-thiones with O-alkenyloxy/alkynyloxy-salicylaldehydes/naphthaldehydes in a Brønsted acidic ionic liquid, [Hmim]HSO\(_4}\), methylimidazolium hydrogen sulphate, under microwave irradiation. The method is simple
A new cascade approach has been developed for the one-pot four-step divergent synthesis of polysubstituted benzofurans and 2H-chromenes, featuring a novel cascade aromatic Claisen rearrangement/Meinwald rearrangement/dehydrative or oxidative cyclization. This new method was demonstrated with 39 examples tolerating different substitutions at an epoxide, allylic ether, and aromatic ring, and we showcased