72471-05-7Relevant academic research and scientific papers
Improved Synthesis of MediPhos Ligands and Their Use in the Pd-Catalyzed Enantioselective N-Allylation of Glycine Esters
Albat, Dominik,Neud?rfl, J?rg-Martin,Reiher, Martin,Schmalz, Hans-Günther
supporting information, p. 4237 - 4242 (2021/08/24)
A new class of chiral C2-symmetric diphosphines (MediPhos) was recently shown to give superior results in the Pd-catalyzed asymmetric N-allylation of amino acid esters. We here describe a new, improved protocol for the preparation of such ligands through bidirectional SN2-coupling of a tartrate-derived ditosylate with 6-alkyl-2-bromophenols followed by double lithiation/phosphanylation. This method gave access to a series of nine ligands with branched alkyl substituents, which were benchmarked in the enantioselective Pd-catalyzed N-allylation of tert-butyl glycinate with racemic (E)-2,8-dimethylnona-5-en-4-yl methyl carbonate (up to 95 % ee). In addition, the analogous transformation of tert-butyl glycinate with methyl (E)-nona-5-en-4-yl carbonate was optimized. The obtained allylic amines were then used in the stereoselective synthesis of the conformationally restricted proline-derived dipeptide analogs ProM-17 and ProM-21.
Cascade Claisen and Meinwald Rearrangement for One-Pot Divergent Synthesis of Benzofurans and 2 H-Chromenes
Song, Liyan,Su, Qian,Lin, Xi,Du, Zhihui,Xu, Huiyou,Ouyang, Ming-An,Yao, Hongliang,Tong, Rongbiao
, p. 3004 - 3009 (2020/04/20)
A new cascade approach has been developed for the one-pot four-step divergent synthesis of polysubstituted benzofurans and 2H-chromenes, featuring a novel cascade aromatic Claisen rearrangement/Meinwald rearrangement/dehydrative or oxidative cyclization. This new method was demonstrated with 39 examples tolerating different substitutions at an epoxide, allylic ether, and aromatic ring, and we showcased its utility with the first total synthesis of natural product liparacid A in seven steps.
Controlling olefin isomerization in the heck reaction with neopentyl phosphine ligands
Lauer, Matthew G.,Thompson, Mallory K.,Shaughnessy, Kevin H.
, p. 10837 - 10848 (2015/01/08)
The use of neopentyl phosphine ligands was examined in the coupling of aryl bromides with alkenes. Di-tert-butylneopentylphosphine (DTBNpP) was found to promote Heck couplings with aryl bromides at ambient temperature. In the Heck coupling of cyclic alkenes, the degree of alkene isomerization was found to be controlled by the choice of ligand with DTBNpP promoting isomerization to a much greater extent than trineopentylphosphine (TNpP). Under optimal conditions, DTBNpP provides high selectivity for 2-aryl-2,3-dihydrofuran in the arylation of 2,3-dihydrofuran, whereas TNpP provided high selectivity for the isomeric 2-aryl-2,5-dihydrofuran. A similar complementary product selectivity is seen in the Heck coupling of cyclopentene. Heck coupling of 2-bromophenols or 2-bromoanilides with 2,3-dihydrofurans affords 2,5-epoxybenzoxepin and 2,5-epoxybenzazepins, respectively.
Synthesis of tricyclic aromatic compounds by the intramolecular Pauson-Khand reaction promoted by molecular sieves
Perez-Serrano, Leticia,Blanco-Urgoiti, Jaime,Casarrubios, Luis,Dominguez, Gema,Perez-Castells, Javier
, p. 3513 - 3519 (2007/10/03)
Pauson-Khand reactions are carried out with different substituted aromatic enynes, yielding tricyclic cyclopentenones related to natural products such as chromenes. Enynes are easily obtained in a two-step approximation from the corresponding salicylaldehydes. The reaction is promoted by dissolved TMANO (trimethylamine N-oxide) and/or 4 A molecular sieves. This new way of induction for the Pauson-Khand reaction increases yields remarkably, allowing the reaction of some substituted alkenes which fail to react in the absence of the zeolite. Isomerization of the double bond of the cyclopentenone ring is observed except when nonterminal triple bonds are used. For trisubstituted alkenes, an interrupted Pauson-Khand process is observed with moderate yields.
Selective Indirect Oxidation of Phenol to Hydroquinone and Catechol
Dai, S. H.,Lin, C. Y.,Rao, D. V.,Stuber, F. A.,Carleton, P. S.,Ulrich, Henri
, p. 1722 - 1725 (2007/10/02)
The introduction of a hydroxyl function into phenol to give hydroquinone and catechol can be achieved in high yields by the reaction of hydrogen peroxide with alkenylphenols.These alkenylphenols are obtained by thermolysis of bisphenol A, alkylation of phenol with cyclopentadiene followed by isomerization, and alkylation of phenol with mesityl oxide followed by thermolysis to give 4-isopropenylphenol, 2- and 4-(cyclopenten-1-yl)phenol, and 2,2,4-trimethyl-1,2-chromene, respectively.
