61747-55-5Relevant academic research and scientific papers
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.
Organoboranes mediated radical cyclizations
Becattini, Barbara,Ollivier, Cyril,Renaud, Philippe
, p. 1485 - 1487 (2007/10/03)
Hydroboration of dienes with catecholborane followed by radical cyclization using pyridine-2-thione-N-methoxycarbonyloxy (= PTOC-OMe, a Barton carbonate) as chain transfer reagent is reported. A facile access to a bicyclic α-methylenelactone is described.
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.
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.
Indium mediated intramolecular carbocyclization in aqueous media. A facile and stereoselective synthesis of fused α-methylene-γ-butyrolactones
Bryan, Vernal J.,Chan, Tak-Hang
, p. 5341 - 5342 (2007/10/03)
Indium mediated intramolecular carbocyclization in aqueous media gave cis-fused α-methylene-γ-butyrolactones selectively in good yields.
Iodomethylene lactone formation. An improved synthesis
Mawson,Routledge,Weavers
, p. 4665 - 4678 (2007/10/02)
Detailed examination of the free radical induced cyclisation of the propiolate ester of trans-2-iodocyclopentanol has revealed a rather inefficient radical chain. The optimum conditions found used dibenzoyl peroxide as initiator and benzene as the reaction solvent. High concentrations of initiator were required and significant quantities of iodobenzene were formed. Portionwise addition of initiator was found to be beneficial, but use of inert atmospheres gave no advantage. Although the reaction was quite highly selective to give predominantly the (E)-iodomethylene lactone, trace quantities of the (Z)-isomer were isolated. Other minor by-products could be attributed to trapping of the intermediate vinyl radical by the solvent. An alternative, improved route to iodomethylene lactones via fluoride ion desilylation of the trimethylsilyl substituted derivatives has been developed.
Photoisomerisation of (E)-Iodoalkylidene Lactones. A Route to (Z)-Iodoalkylidene Lactones
Haaima, Gerald,Hanton, Lyall R.,Lynch, Mary-Jeanne,Mawson, Simon D.,Routledge, Anne,Weavers, Rex T.
, p. 2161 - 2174 (2007/10/02)
Photochemically induced free-radical cyclisation of iodo acetylenic esters provides low yields of mixtures from which both (E)- and (Z)-iodoalkylidene lactones may be isolated.However, photoisomerisation of (E)-iodoalkylidene lactones, which have previously been obtained in good yields by dibenzoyl peroxide induced cyclisation of iodo acetylenic esters, provides (E)/(Z)-mixtures from which the previously inaccessible (Z)-isomers may be isolated by chromatography.Also reported is a collection of IR, UV and NMR spectral data, all of which provide useful information relating to the stereochemistry of the iodoalkylidene lactones.A comparison of the cryctal structures of the (E)- and (Z)-isomers of a trimehylsilyl iodomethylene lactone is also included.
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.
ALKYLIDENE LACTONE SYNTHESIS
Haaima, Gerald,Lynch, Mary-Jeanne,Routledge, Anne,Weavers, Rex T.
, p. 5203 - 5214 (2007/10/02)
The iodoalkylidene lactones formed by reaction of alkenes with acetylenic acids in the presence of N-iodosuccinimide and subsequent free radical cyclisation, can be de-iodinated photochemically or alkylated with lithium diorganocuprate reagents to yield a variety of α-alkylidene lactones.
