623-48-3Relevant articles and documents
Infrared spectroscopic studies of the conformation in ethyl α-haloacetates in the vapor, liquid and solid phases
Jassem, Naserallah A.,El-Bermani, Muhsin F.
, p. 213 - 223 (2010)
Infrared spectra of ethyl α-fluoroacetate, ethyl α-chloroacetate, ethyl α-bromoacetate and ethyl α-iodoacetate have been measured in the solid, liquid and vapor phases in the region 4000-200 cm-1. Vibrational frequency assignment of the observed bands to the appropriate modes of vibration was made. Calculations at DFT B3LYP/6-311+G** level, Job: conformer distribution, using Spartan program '08, release 132 was made to determine which conformers exist in which molecule. The results indicated that the first compound exists as an equilibrium mixture of cis and trans conformers and the other three compounds exist as equilibrium mixtures of cis and gauche conformers. Enthalpy differences between the conformers have been determined experimentally for each compound and for every phase. The values indicated that the trans of the first compound is more stable in the vapor phase, while the cis is the more stable in both the liquid and solid phases. In the other three compounds the gauche is more stable in the vapor and liquid phases, while the cis conformer is the more stable in the solid phase for each of the second and third compound, except for ethyl α-iodoacetate, the gauche conformer is the more stable over the three phases. Molar energy of activation Ea and the pseudo-thermodynamic parameters of activation ΔH?, ΔS? and ΔG? were determined in the solid phase by applying Arrhenius equation; using bands arising from single conformers. The respective Ea values of these compounds are 5.1 ± 0.4, 6.7 ± 0.1, 7.5 ± 1.3 and 12.0 ± 0.6 kJ mol-1. Potential energy surface calculations were made at two levels; for ethyl α-fluoroacetate and ethyl α-chloroacetate; the calculations were established at DFT B3LYP/6-311+G** level and for ethyl α-bromoacetate and ethyl α-iodoacetate at DFT B3LYP/6-311G* level. The results showed no potential energy minimum exists for the gauche conformer in ethyl α-fluoroacetate.
Forskolin Editing via Radical Iodo- A nd Hydroalkylation
Pruteanu, Elena,Tappin, Nicholas D. C.,G?rbu, Vladilena,Morarescu, Olga,Dénès, Fabrice,Kulci?ki, Veaceslav,Renaud, Philippe
, p. 1247 - 1261 (2021)
The modification of highly oxygenated forskolin as well as manoyl and epi-manoyl oxide, two less functionalized model substrates sharing the same polycyclic skeleton, via intermolecular carbon-centered radical addition to the vinyl moiety has been investigated. Highly regio- A nd reasonably stereoselective iodine atom transfer radical addition (ATRA) reactions were developed. Unprotected forskolin afforded an unexpected cyclic ether derivative. Protection of the 1,3-diol as an acetonide led the formation of the iodine ATRA product. Interestingly, by changing the mode of initiation of the radical process, in situ protection of the forskolin 1,3-diol moiety as a cyclic boronic ester took place during the iodine ATRA process without disruption of the radical chain process. This very mild radical-mediated in situ protection of 1,3-diol is expected to be of interest for a broad range of radical and non-radical transformations. Finally, by using our recently developed tert-butyl?-catechol-mediated hydroalkylation procedure, highly efficient preparation of forskolin derivatives bearing an extra ester or sulfone group was achieved.
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Voronkov,Lapina
, (1970)
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Methyl Radical Initiated Kharasch and Related Reactions
Tappin, Nicholas D. C.,Renaud, Philippe
supporting information, p. 275 - 282 (2020/12/07)
An improved procedure to run halogen atom and related chalcogen group transfer radical additions is reported. The procedure relies on the thermal decomposition of di-tert-butylhyponitrite (DTBHN), a safer alternative to the explosive diacetyl peroxide, to produce highly reactive methyl radicals that can initiate the chain process. This mode of initiation generates byproducts that are either gaseous (N2) or volatile (acetone and methyl halide) thereby facilitating greatly product purification by either flash column chromatography or distillation. In addition, remarkably simple and mild reaction conditions (refluxing EtOAc during 30 minutes under normal atmosphere) and a low excess of the radical precursor reagent (2 equivalents) make this protocol particularly attractive for preparative synthetic applications. This initiation procedure has been demonstrated with a broad scope since it works efficiently to add a range of electrophilic radicals generated from iodides, bromides, selenides and xanthates over a range of unactivated terminal alkenes. A diverse set of radical trap substrates exemplifies a broad functional group tolerance. Finally, di-tert-butyl peroxyoxalate (DTBPO) is also demonstrated as alternative source of tert-butoxyl radicals to initiate these reactions under identical conditions which gives gaseous by-products (CO2). (Figure presented.).
Decarboxylative (4+1) Oxidative Annulation of Malonate Monoesters with 2-Vinylpyridine Derivatives
Tang, Shan,Gao, Xinlong,Lei, Aiwen
supporting information, p. 2878 - 2882 (2016/09/16)
A novel N-iodosuccinimide-mediated decarboxylative (4+1) oxidative annulation between 2-vinylpyridine derivatives and malonate monoesters was developed. It offers a new way to construct indolizine derivatives by utilizing malonate monoesters as a C1unit. The alkyl 2,2-diiodoacetate was found to be the active reaction intermediate during the transformation. (Figure presented.).
