Synthesis of .gamma.- and .delta.-lactones by free-radical annelation of Se-phenyl selenocarbonates
摘要:
A general method for the synthesis of gamma- and delta-lactones through the intramolecular addition of alkoxycarbonyl radicals, formed by reaction of Se-phenylselenocarbonates with n-Bu3SnH, onto carbon-carbon multiple bonds is described. This free-radical cyclization is characterized by high regioselectivity favoring exo addition and by a high ratio of cyclization to reduction. Monocyclic, fused bicyclic, and spirocyclic lactones are formed in good to excellent yield. Use of allyltri-n-butyltin as a chain-transfer agent in the place of n-Bu3SnH affords the corresponding 3-butenyl lactones.
Unprecedented <i>E</i>-stereoselectivity on the sigmatropic Hurd–Claisen rearrangement of Morita–Baylis–Hillman adducts: a joint experimental–theoretical study
作者:Vinicius Sobral Silva、Terezinha Alves Tolentino、Tiago Costa Alves Fontoura Rodrigues、Fernanda Ferrari Martins Santos、Daniel Francisco Scalabrini Machado、Wender Alves Silva、Heibbe Cristhian Benedito de Oliveira、Angelo Henrique Lira Machado
DOI:10.1039/c9ob00533a
日期:——
first systematic investigation of the tandem mercury(II) catalysed transvinylation/Hurd–Claisen rearrangement of MBH adducts derived from alkyl acrylates. This is the first report of E-selectivity for MBH adducts with alkyl side chains and is complementary to the previously reported Johnson–Claisen and Eschenmoser–Claisen rearrangements. The rearrangement products were obtained in good yields and could
Copper-Catalyzed Desaturation of Lactones, Lactams, and Ketones under pH-Neutral Conditions
作者:Ming Chen、Guangbin Dong
DOI:10.1021/jacs.9b07932
日期:2019.9.18
A copper-catalyzed desaturation method is reported, which is suitable for converting lactones, lactams and cyclic ketones to their α,β-unsaturated counterparts. The reaction does not require strong base/acid or sulfur/selenium reagents, and can be carried out through a simple one-step operation. The protocol uses inexpensive catalysts and reagents, exhibits excellent scalability and functional group
报道了一种铜催化的去饱和方法,该方法适用于将内酯、内酰胺和环酮转化为它们的 α,β-不饱和对应物。该反应不需要强碱/酸或硫/硒试剂,可通过简单的一步操作进行。该协议使用廉价的催化剂和试剂,具有出色的可扩展性和官能团耐受性。值得注意的是,叔丁醇是唯一产生的化学计量副产物,并且没有观察到过度氧化。通过对照实验、氘标记、自由基钟、EPR、HRMS 和动力学研究研究了反应机理。获得的数据与涉及可逆α-去质子化的反应途径一致,Cu(II)-OtBu 物种,然后进一步氧化所得的 Cu 烯醇化物。
Highly Enantioselective Iridium-Catalyzed Hydrogenation of α,β-Unsaturated Esters
作者:Jia-Qi Li、Xu Quan、Pher G. Andersson
DOI:10.1002/chem.201200907
日期:2012.8.20
α,β‐Unsaturated esters have been employed as substrates in iridium‐catalyzed asymmetric hydrogenation. Full conversions and good to excellent enantioselectivities (up to 99 % ee) were obtained for a broad range of substrates with both aromatic‐ and aliphatic substituents on the prochiral carbon. The hydrogenated products are highly useful as building blocks in the synthesis of a variety of natural
study antifungal activities. In vitro and in vivo antifungal activity results revealed that compounds 2-25, which contain a γ-butyrolactone scaffold and cinnamic aldehyde moiety, have greater potent fungicidal activity than other compounds. The preliminary structure–activity relationships (SARs) demonstrated that compounds with electron-withdrawing groups and small steric hindrance would have more desirable
Custom synthesis of substituted butenolides, dihydropyranones, and α-E-alkylidenelactones via alkenylalumination
作者:P. Veeraraghavan Ramachandran、Debarshi Pratihar、Garrett Garner、B. China Raju
DOI:10.1016/j.tetlet.2011.06.103
日期:2011.9
trifluoroacetic acid lactonizes to furnish α-acetoxyalkyl butenolides (n = 1) and dihydropyranones (n = 2) in 40% overall yield. Conjugateaddition to these lactenones and concurrent acetate elimination constitute a general and stereospecificsynthesis of the corresponding α-E-alkylidene lactones.