78684-19-2Relevant academic research and scientific papers
Strain-Driven Dyotropic Rearrangement: A Unified Ring-Expansion Approach to α-Methylene-γ-butyrolactones
Lei, Xiaoqiang,Li, Yuanhe,Lai, Yang,Hu, Shengkun,Qi, Chen,Wang, Gelin,Tang, Yefeng
supporting information, p. 4221 - 4230 (2020/12/22)
An unprecedented strain-driven dyotropic rearrangement of α-methylene-β-lactones has been realized, which enables the efficient access of a wide range of α-methylene-γ-butyrolactones displaying remarkable structural diversity. Several appealing features of the reaction, including excellent efficiency, high stereospecificity, predictable chemoselectivity and broad substrate scope, render it a powerful tool for the synthesis of MBL-containing molecules of either natural or synthetic origin. Both experimental and computational evidences suggest that the new variant of dyotropic rearrangements proceed in a dualistic pattern: while an asynchronous concerted mechanism most likely accounts for the reactions featuring hydrogen migration, a stepwise process involving a phenonium ion intermediate is favored in the cases of aryl migration. The great synthetic potential of the title reaction is exemplified by its application to the efficient construction of several natural products and relevant scaffolds.
Synthesis of α-methylene-γ-lactone structure by cyclization of ω-formylallylsilane in water
Fukushima, Hiroki,Ikegami, Daisuke,Kuroda, Chiaki,Kobayashi, Kenichi
, p. 568 - 574 (2018/05/07)
Surfactant-type protonic acid-promoted intramolecular cyclization of functionalized allylsilanes was studied in water for the synthesis of α-methylene-γ-lactone compounds. ω-Formyl-β-(acetoxymethyl)allylsi-lane afforded carbocyclic compounds in good yields, while the cyclization product was not obtained from the corresponding β-ethoxycarbonyl derivative. It was found that (Z)-β-(acetoxymethyl)allylsilane predominantly afforded the cis-product, while (E)-β-(acetoxymethyl)allylsilane afforded both cis- and trans-products at a ratio of almost 1:1. The stereoselectivity of the cyclization reaction was almost the same as a protonic acid-promoted reaction in CH2Cl2 and was explained by an interaction between the C(Si)–C(alkene) bond and the carbonyl moiety. The cyclization products were converted to α-methylene-γ-lactone compounds.
Synthesis of bicyclic γ-butyrolactone derivatives by rhodium catalyzed intramolecular C-H insertion of α-dizao α-phosphoryl cycloalkyl esters
Shie, Jr-Yun,Zhu, Jia-Liang
, p. 1590 - 1601 (2016/03/01)
Under the catalysis of Rh2(OAc)4, several readily prepared cycloalkyl α-diazo α-phosphoryl esters undergo a intramolecular C-H insertion reaction to afford the fused bicyclic α-phosphoryl-γ-butyrolactones in varying yields (10%-80%) and dr ratios (69:14:17 to >99:1). The experimental results reveal that the reactivity of the precursors and the diastereoselectivity of the cyclization are both influenced by the ring sizes of the cycloalkyl moieties. Moreover, most of the resulting products can be further elaborated into α,α-dialkyl γ-butyrolactones via a two-step alkylation/reductive alkylation sequence with the controlled installation of two alkyl groups to the lactones. In addition, application of Horner-Wadsworth-Emmons (HWE) olefination reaction to the insertion products allows an access to bicyclic α-alkylidene-γ-butyrolactone ring systems that occur ubiquitously in biologically active natural products and synthetic molecules.
α-Alkylidene-γ-butyrolactone synthesis via one-pot C-H insertion/olefination: substrate scope and the total synthesis of (±)-cedarmycins A and B
Lloyd, Matthew G.,D'Acunto, Mariantonietta,Taylor, Richard J.K.,Unsworth, William P.
, p. 7107 - 7123 (2015/02/19)
Abstract A system for the synthesis of α-alkylidene-γ-butyrolactones via a one-pot C-H insertion/olefination sequence is described. The process is based on the rhodium catalysed C-H insertion reaction of α-diazo-α-(diethoxyphosphoryl)acetates. The mild reaction conditions, operational simplicity and ready availability of starting materials are all key features. A wide range of successful reaction systems are reported (41 examples) highlighting the generality of the method. The application of this method in the total synthesis of the natural products (±)-cedarmycins A and B is also described.
Dibromomethane as one-carbon source in organic synthesis: A versatile methodology to prepare the cyclic and acyclic α-methylene or α-keto acid derivatives from the corresponding terminal alkenes
Hon, Yung-Son,Liu, Yu-Wei,Hsieh, Cheng-Han
, p. 4837 - 4860 (2007/10/03)
Ozonolysis of mono-substituted alkenes A-1 followed by reacting with a preheated mixture of CH2Br2-Et2NH affords α-substituted acroleins A-2 in good yields. Under very mild reaction conditions, these α-substituted acroleins A-2 can be easily converted to α-methylene esters A-4, which could be further converted to the corresponding α-keto esters A-5. This methodology can be also applied to the preparation of α-methylene lactones B-4, α-methylene lactams, and α-keto lactones B-5 with various ring sizes.
Carbonylation of alkynols catalyzed by Pd(II)/2-PyPPh2 dissolved in organic solvents and in ionic liquids: A facile entry to α-methylene γ- and δ-lactones
Consorti, Crestina S,Ebeling, Gunter,Dupont, Jaírton
, p. 753 - 755 (2007/10/03)
The carbonylation of terminal 3-alkyn-1-ols and 1-alkyn-4-ols by Pd(OAc)2 associated with 2-(diphenylphosphino)pyridine (2-PyPPh2) dissolved in organic solvents or in 1-n-butyl-3-methyl imidazolium ionic liquids affords quantitatively and selectively exo-α-methylene γ- and δ-lactones, respectively. In the case of the reactions performed in ionic liquids (biphasic conditions), the lactones were isolated by simple distillation and the ionic catalyst solution can be reused.
Synthesis of bicyclic α-methylene butyrolactones via alkoxycarbonylation of molybdenum-propargyl compounds
Shieh, Shwu-Ju,Liu, Rai-Shung
, p. 5209 - 5212 (2007/10/03)
Syntheses of various bicyclic α-methylene butyroladones from functionalized propargyl bromides were carried out in short steps, the overall yields are reasonable. The key step involves alkoxycarbonylation of molybdenum-propargyl compounds.
Tungsten-Mediated Syntheses of Fused α-Methylenebutyrolactones from Propargyl Bromides Containing Tethered Aldehydes and Ketones
Shieh, Shwu-Ju,Chen, Chi-Chung,Liu, Rai-Shung
, p. 1986 - 1990 (2007/10/03)
The reaction of CpW(CO)3Na with a number of propargyl bromides with tethered aldehydes and ketones afforded η1-propargyl species that were subsequently transformed into tungsten-η3-2-(methoxycarbonyl)allyl compounds upon treatment with p-TSA/CH3OH; the overall yields exceeded 60%. Sequential treatment of these tungsten-η3-allyl complexes with NOBF4 and NaI in CH3CN led to intramolecular allyltungsten-carbonyl cyclization, yielding fused α-methylene butyrolactones of five-, six-, and seven-membered carbocyclic rings. All the reactions proceeded with high diastereoselectivities except for 9-methylene-7-oxabicyclo[4.3.0]nonan-8-one (22) and 10-methylene-8-oxabicyclo[5.3.0]decan-9-one (23). Modification of the metal center with a chloride ligand led to significant improvement of the trans-stereoselection of 22; the chloride modification did not significantly enhance stereoselection of 23. The stereochemical course of the reaction products is rationalized on the basis of a bicyclic transition-state mechanism.
Dehaloalkoxycarbonylations Reactions. Part VI. An Approach to the Synthesis of Fused α-Methylene-γ-Butyrolactones
Bukowska, M.,Prejzner, J.
, p. 699 - 702 (2007/10/02)
A simple procedure for the preparation of fused α-methylene-γ-butyrolactones illustrated by the syntheses of cis- and trans-hexahydro-3-methylene-2(3H)-benzofuranone (3c and 3t) based on the dehydrated-alumina-catalysed β-debromomethoxycarbonylation reaction of the corresponding cis- and trans-octahydrobenzo-3-bromomethyl-2-oxo-3-benzofurancarboxylic methyl esters (2c and 2t) as model compounds has been described.Key words: γ-butyrolactones, bromomethylation, β-dehaloalkoxycarbonylation
Stereoselective intramolecular cyclization of β-alkoxycarbonyl-ω-formylallylsilanes into bicyclic α-methylene-γ-lactones
Nishitani,Nakamura,Orii,Arai,Yamakawa
, p. 822 - 831 (2007/10/02)
α-Methylene-γ-lactones fused to five- and six-membered carbocycles were efficiently synthesized from β-ethoxycarbonyl-ω-formylallylsilane derivatives by means of the intramolecular Hosomi reaction. The formylated allylsilanes (11a, b, 12a and b) were synthesized from ethyl β-trimethylsilylpropionate and ω-tetrahydropyranyloxypentanal (4a) and -hexanal (4b) in several steps. The cyclization reaction of these aldehydes was performed under mild conditions with a high degree of stereocontrol. Treatment of the (E)- and (Z)-isomers of the allylsilanes (11a and 12a) with titanium tetrachloride or boron trifluoride etherate gave a five-membered cis-hydroxy ester (13a). Treatment of the (Z)-allylsilane derivative (11b) with titanium tetrachloride afforded a six-membered cis-hydroxy ester (13b) as a major product together with the trans-isomer (14b), and treatment with boron trifluoride etherate selectively gave the cis-isomer (13b). On the other hand, treatment of (E)-allylsilane (12b) with titanium tetrachloride selectively gave the cis-hydroxy ester (13b), while the use of boron trifluoride etherate exclusively afforded the trans-isomer (14b). These stereoselectivities can be explained in terms of chelated transition models. Lactonization of these hydroxy esters afforded the corresponding fused α-methylene-γ-lactones (16a, 17a and b) in good yields.
