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1.
[reaction: see text]. Palladium-catalyzed electrophilic allylic substitution of functionalized allyl chlorides and allyl acetates can be achieved in the presence of hexamethylditin under mild reaction conditions. The substitution reaction occurs with very high regioselectivity at the branched allylic terminus. Regioselective tandem bisallylation reaction could be performed by employing benzylidenemalonitrile as substrate. The reaction mechanism can be explained by involvement of a bisallylpalladium intermediate. A particularly interesting mechanistic feature of this reaction is that palladium catalyzes up to three different transformations in the same catalytic cycle. DFT calculations indicate that the regioselectivity is determined by the location of the allylic substituent in the eta1-allyl moiety of the reaction intermediate. 相似文献
2.
A highly regioselective palladium-catalyzed allylic alkylation of fluorobis(phenylsulfonyl)methane has been studied. Using different allylic carbonates, a variety of terminal mono-fluoromethylated compounds were achieved in 85-99% yields with high regioselectivities. 相似文献
3.
Rana Chatterjee Satyajit Samanta Anindita Mukherjee Sougata Santra Grigory V. Zyryanov Adinath Majee 《Tetrahedron letters》2019,60(3):276-283
We have observed that the allylic zinc halide under identical reaction conditions acts in different modes for different electrophiles. For Ts-aziridines the halide part of the allylic halide has been introduced as a nucleophile and for the carbonyl compounds the simple allylation reaction occurs. To the best of our knowledge this is the first report where the allylic zinc halide is the source of halide acting as nucleophile. The main advantages of the present procedure are easy to handle, no need of inert atmosphere, mild reaction conditions, and applicability to a wide variety of substrates for aziridines and carbonyl compounds. 相似文献
4.
The metalation of allyl benzyl thioether involves the benzylic or the allylic hydrogens. The benzylic carbanion undergoes a rapid[2,3] sigmatropic shift whereas the allylic carbanion gives rise to various rearrangements, among them migration of the allylic unit to the para position with allylic inversion. The temperature dependence of the ratio of products arising from the benzylic carbanion vs those from the allylic carbanion shows that the allylic-to-benzylic carbanion transformation occurs only under special conditions: (a) with slow addition of the base; (b) with thioether in excess relative to the base, and (c) on raising the temperature of the reaction medium from ?78° to ?15°. In the last instance, the proton transfer is intramolecular as shown with labeled thioethers. The extent of the different rearrangements depends on the temperature and solvent. A choice of mechanism cannot be made at this time for the para migration 5→9a. A leaving group effect on the reaction regioselectivity of the carbanion from allyl methyl thioether with benzyl halides has been noticed. The presence of dibenzyl indicates that, in addition to SN2 reactions, some electron transfer process is occurring. 相似文献
5.
Arylation of allylic acetates employing triarylbismuths as multi-coupling reagents under palladium-catalyzed conditions was reported. Triarylbismuths as nucleophilic coupling partners were used in sub-stoichiometric amounts with respect to allylic acetates and thus served as atom-efficient multi-coupling reagents. A variety of allylic acetates were cross-coupled with triarylbismuths to furnish the corresponding functionalized 1,3-disubstituted propenes in good to excellent yields in short reaction times. The reported palladium protocol also yielded chemo-selective allylic arylations in high yields. 相似文献
6.
Martín-Matute B Bogár K Edin M Kaynak FB Bäckvall JE 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(20):5832-5842
A range of ruthenium cyclopentadienyl (Cp) complexes have been prepared and used for isomerization of allylic alcohols to the corresponding saturated carbonyl compounds. Complexes bearing CO ligands show higher activity than those with PPh3 ligands. The isomerization rate is highly affected by the substituents on the Cp ring. Tetra(phenyl)methyl-substituted catalysts rapidly isomerize allylic alcohols under very mild reaction conditions (ambient temperature) with short reaction times. Substituted allylic alcohols have been isomerized by employing Ru-Cp complexes. A study of the isomerization catalyzed by [Ru(Ph5Cp)(CO)2H] (14) indicates that the isomerization catalyzed by ruthenium hydrides partly follows a different mechanism than that of ruthenium halides activated by KOtBu. Furthermore, the lack of ketone exchange when the isomerization was performed in the presence of an unsaturated ketone (1 equiv), different from that obtained by dehydrogenation of the starting allylic alcohol, supports a mechanism in which the isomerization takes place within the coordination sphere of the ruthenium catalyst. 相似文献
7.
Catalytic and enantioselective synthesis of amino acids is a subject of intense interest in the field of asymmetric catalysis. Traditionally, researchers have concentrated their efforts largely on the design and discovery of enantiopure catalysts for the Strecker reaction, alkylation of tert-butyl gylcinate-benzophenone, electrophilic amination of carbonyl compounds, and hydrogenation of N-acyl-aminoacrylic acid; however, the scope of these reactions is limited. In this paper, we report on a different approach to amino acids based on an expeditious route to enantiopure allylic amines. A highly enantioselective and catalytic vinylation of aldehydes leads to allylic alcohols that are then transformed to the allylic amines via Overman's [3,3]-sigmatropic rearrangement of imidates. Oxidative cleavage of the allylic amines furnishes the amino acids in good yields and excellent ee's. The scope and utility of this method are demonstrated by the synthesis of challenging allylic amines and their subsequent transformation to valuable nonproteinogenic amino acids, including both D and L configured (1-adamantyl)glycine. 相似文献
8.
9.
A cross ene-yne metathesis has been achieved at a nearly 1:1 stoichiometry of the unsaturated reactants. This allowed the use of more complex alkene reactants without sacrificing excess alkene reactant. In the alkene, different allylic oxygen protecting groups were explored. Interestingly, alkenes containing the allylic hydroxyl group proved to be the most reactive. 相似文献
10.
Greice Tabarelli Marcelo Godoi Rômulo F. S. Canto José R. Mora Faruk Nome 《合成通讯》2014,44(23):3441-3449
We present herein a new catalyst-free and solvent-free approach for the synthesis of allylic thioethers directly from allylic alcohols and thiols. The methodology allows the synthesis of different allylic thioethers in good to excellent yields under microwave irradiation. Theoretical calculations for the allylic carbocation helped to explain the regioselectivity observed when nonsymmetric substrates are used in the reaction. 相似文献
11.
Iridium-catalyzed allylic vinylation and asymmetric allylic amination reactions with o-aminostyrenes
Ye KY He H Liu WB Dai LX Helmchen G You SL 《Journal of the American Chemical Society》2011,133(46):19006-19014
An Ir-catalyzed allylic vinylation reaction of allyl carbonates with o-aminostyrene derivatives has been realized, providing skipped (Z,E)-diene derivatives. With (E)-but-2-ene-1,4-diyl dimethyl dicarbonate as the substrate, an efficient enantioselective synthesis of 1-benzazepine derivatives via an Ir-catalyzed domino allylic vinylation/intramolecular allylic amination reaction has been developed. Mechanistic studies of the allylic vinylation reaction have been carried out, and the results suggest that the leaving group of the allylic precursor plays a key role in directing the reaction pathway. Screening of various allylic precursors showed that Ir-catalyzed reactions of allyl diethyl phosphates with o-aminostyrene derivatives proceed via an allylic amination pathway. A subsequent ring-closing metathesis (RCM) reaction of the amination products led to a series of enantiomerically enriched 1,2-dihydroquinoline derivatives. Their utility is indicated by an asymmetric total synthesis of (-)-angustureine. 相似文献
12.
[reaction: see text] A useful method for the conversion of prochiral allylic alcohols to chiral allylic amines of high enantiopurity is reported. N-(4-Methoxyphenyl)trifluoroacetimidates are excellent substrates for the palladium(II)-catalyzed allylic imidate rearrangement as the allylic trifluoroacetamide products can be deprotected in two steps to provide chiral nonracemic allylic amines. Di-mu-chlorobis[(eta(5)-(S)-(pR)-2-(2'-(4'-isopropyl))oxazolinylcyclopentadienyl,1-C,3'-N))(eta(4)-tetraphenylcyclobutadiene)cobalt]dipalladium (6a, COP-Cl) is a superior catalyst because it does not require activation with silver salts and provides rearranged allylic trifluoroacetamides in good yields and high enantiomeric purities. 相似文献
13.
A palladium-catalyzed asymmetric allylation of isatins with allylic alcohols as an allyl donor was developed by using chiral spiro phosphoramidite ligands. A variety of chiral tertiary homoallylic alcohols 3-allyl-3-hydroxy-2-oxindoles were prepared directly from allylic alcohols in one step with excellent yields and moderate enantioselectivities. This represents the first catalytic asymmetric allylation of ketones with allylic alcohol as the allylating agent. 相似文献
14.
A series of N-protected beta-amino phosphonic acid esters have been prepared by phosphine-catalyzed allylic substitution of 2-(diethylphosphonyl)-substituted allylic acetates employing 4,5-dichlorophthalimide as nucleophilic partner. These organocatalytic allylic substitutions exhibit exceptionally high levels of regiospecificity by virtue of a tandem S(N)2'-S(N)2' mechanism. 相似文献
15.
《Tetrahedron letters》1987,28(48):5973-5976
A radical-based cyclization is described that employs xanthates or cyclic thionocarbonates as initiators and allylic dithiocarbonates or allylic thiocarbamates as terminators. 相似文献
16.
Silicon‐Directed Rhenium‐Catalyzed Allylic Carbaminations and Oxidative Fragmentations of γ‐Silyl Allylic Alcohols
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Dr. Sanjay W. Chavhan Dr. Matthew J. Cook 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(17):4891-4895
A highly regioselective allylic substitution of β‐silyl allylic alcohols has been achieved that provides the branched isomer as a single product. This high level of regiocontrol is achieved through the use of a vinyl silane group that can perform a Hiyama coupling providing 1,3‐disubstituted allylic amines. An unusual oxidative fragmentation product was also observed at elevated temperature that appears to proceed by a Fleming–Tamao‐type oxidation–elimination pathway. 相似文献
17.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(32):9645-9649
A catalytic intermolecular allylic C−H trifluoromethoxylation reaction of alkenes has been developed based on the use of a palladium catalyst, CsOCF3 as the trifluoromethoxide source, and benzoquinone as the oxidant. This reaction provides an efficient route for directly accessing allylic trifluoromethoxy derivatives with excellent regioselectivities from terminal alkenes via an allylic C−H bond activation process. 相似文献
18.
Stereoselective and diversity-oriented synthesis of trisubstituted olefins was achieved by using ortho-diphenylphosphanyl benzoate (o-DPPB) as a directing group for allylic substitution. The starting point of this methodology was a set of α-methylene aldehydes derived from Baylis-Hillman adducts. Subsequent addition of different organometallic reagents led to a variety of allylic alcohol substrates. After introduction of the reagent-directing o-DPPB group, copper-mediated allylic substitution with a wide range of Grignard reagents enabled the stereoselective construction of a large number of E-configured trisubstituted allylic alcohols and amines in excellent yields and stereoselectivities. Remarkable is the synthetic flexibility, which allows a wide range of permutations starting from an aldehyde followed by successive introduction of the substituents R(2) and R(3) from organometallic Grignard based reagents. Thus, starting from only a few precursors, a diversity-oriented synthesis of stereodefined trisubstituted allylic alcohols and amines becomes possible. 相似文献
19.
A highly chemoselective oxidation of allylic and vinylic sulfides to the corresponding sulfoxides has been developed using flavin 1 as the oxidation catalyst and hydrogen peroxide as the terminal oxidant. The sulfoxides were formed in good to excellent yields in a highly selective manner even when an excess of the oxidant was used. Sulfone formation was completely suppressed to <0.5% (in one single case 1.5% sulfone was detected). No epoxidation of double bonds or interference with other functional groups was observed under the reaction conditions. The general applicability was demonstrated by the selective oxidation of various allylic and vinylic sulfides having different electronic properties. A number of functionalities including hydroxy, acetoxy, amino, silyloxy, and formyl groups are tolerated under these mild reaction conditions. 相似文献
20.
Lukas J. Hilpert Bernhard Breit 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(29):10044-10048
A rare case of a parallel kinetic resolution of racemic 1,3‐disubstituted allenes by means of a rhodium‐catalyzed addition to 1,3‐diketones furnishing enantiopure allylic 1,3‐diketones is described. Mechanistic experiments demonstrate that the different allene enantiomers react in parallel to either the diastereomeric E‐ or Z‐allylic 1,3‐diketones with the same absolute configuration of the newly formed stereogenic center. A broad substrate scope demonstrates the synthetic utility of this new method. 相似文献