Cobalt-Catalyzed Allylic C(sp<sup>3</sup>)–H Carboxylation with CO<sub>2</sub>
作者:Kenichi Michigami、Tsuyoshi Mita、Yoshihiro Sato
DOI:10.1021/jacs.7b02775
日期:2017.5.3
tolerability, so that selective addition to CO2 occurred in the presence of other carbonyl groups such as amide, ester, and ketone. Since styrylacetic acidderivatives can be readily converted into optically active γ-butyrolactones through Sharpless asymmetric dihydroxylation, this allylic C(sp3)-H carboxylation showcases a facile synthesis of γ-butyrolactones from simple allylarenes via short steps.
借助 Co/Xantphos 复合物开发了末端烯烃的烯丙基 C(sp3)-H 键与 CO2 的催化羧化。广泛的烯丙基芳烃和 1,4-二烯以中等至高产率成功转化为线性苯乙烯乙酸和六-3,5-二烯酸衍生物,并具有出色的区域选择性。羧化显示出显着的官能团耐受性,因此在其他羰基(如酰胺、酯和酮)存在的情况下,会发生选择性加成到 CO2 中。由于苯乙烯乙酸衍生物可以通过 Sharpless 不对称二羟基化很容易地转化为光学活性的 γ-丁内酯,这种烯丙基 C(sp3)-H 羧化展示了从简单的烯丙基芳烃通过短步骤轻松合成 γ-丁内酯。
Synthesis of isochroman-3-ylacetates and isochromane-γ-lactones through rearrangement of aryldioxolanylacetates
作者:Robin G. F. Giles、Rodney W. Rickards、Badra S. Senanayake
DOI:10.1039/a807005i
日期:——
Lewisacid catalysed rearrangement of methyl 4,5-trans-4-aryldioxolan-5-ylacetates 1 provides a convenientroute to substituted methyl isochroman-3-ylacetates 2 and isochromane-γ-lactones 3. The choice of Lewisacid is determined by the substitution pattern of the aromatic ring. The two contiguous isochromane stereocentres are transferred unchanged from the parent dioxolanes, while the configuration
Reaction of 2-butenoic acid dianion and its N-(4-methoxyphenyl)amide with methoxy-substituted arynes
作者:Abdul Rakeeb Deshmukh、Tran Long、Edward R. Biehl
DOI:10.1021/jo00028a049
日期:1992.1
N-(4-Methoxyphenyl)-1-butenamide dianion (6), generated by the reaction of N-(4-methoxyphenyl)-2-butenamide (3) with LDA or LTMP, undergoes exclusive 4-arylation with various methoxy-substituted arynes 2a-e yielding mixtures consisting of a N-(4-methoxyphenyl)-(E)-4-aryl-3-butenamide 9 (85-90%) and a N-(4-methoxyphenyl)-(E)-4-aryl-2-butenamide 9' (10-15%). Under certain conditions, 4,4-diarylated products 12 are also obtained. 2-Butenoic acid dianion (14) also reacts with methoxy-substituted arynes affording predominantly 4-aryl-3-butenoic acids 15 and minor amounts of 4-aryl-2-butenoic acids 15'. The exclusive low temperature (-30 to -40-degrees-C) 4-addition of arynes to dianion 14 is in contrast to the predominant 2-addition that 14 undergoes with certain aldehydes and ketones at comparable temperatures. The mixtures of 4-arylbutenoic acids 15 and 15' and 4-arylbutenamides 9 and 9' were readily hydrogenated (Pd/C) and esterified (MeOH/H2SO4) to synthetically valuable methyl 4-arylbutanoates 17.
Synthesis of the AB-Ring Pyranolactone Substructure of Granaticin A
作者:Ruben Bartholomäus、Janina Bachmann、Christian Mang、Lars Ole Haustedt、Klaus Harms、Ulrich Koert
DOI:10.1002/ejoc.201201279
日期:2013.1
A synthesis of the AB-ring substructure of granaticin A was developed. The pyranolactone moiety was stereoselectively accessed by Sharpless asymmetric dihydroxylation and subsequent oxa-Pictet–Spengler cyclization. The use of BF3·OEt2 resulted in the formation of the cis pyranolactone, whereas the combination of BF3·OEt2 with trifluoroacetic acid led to the trans isomer. The resulting hydroquinones
开发了granaticin A的AB环亚结构的合成。通过 Sharpless 不对称二羟基化和随后的 oxa-Pictet-Spengler 环化,可以立体选择性地获得吡喃内酯部分。BF3·OEt2 的使用导致了顺式吡喃内酯的形成,而BF3·OEt2 与三氟乙酸的结合导致了反式异构体的形成。所得氢醌通过臭氧分解选择性裂解为二羧酸。芳基格氏试剂可以区域选择性地添加到不对称酸酐中。作为构建 B 环的替代策略,可以建立苯-呋喃环加成反应。