97826-89-6Relevant academic research and scientific papers
Backbone-Modified Bisdiazaphospholanes for Regioselective Rhodium-Catalyzed Hydroformylation of Alkenes
Wildt, Julia,Brezny, Anna C.,Landis, Clark R.
, p. 3142 - 3151 (2017/09/05)
A series of tetraaryl bisdiazaphospholane (BDP) ligands were prepared varying the phosphine bridge, backbone, and substituents in the 2- and 5-positions of the diazaphospholane ring. The parent acylhydrazine backbone was transformed to an alkylhydrazine via a borane reduction procedure. These reduced ligands contained an all sp3 hybridized ring mimicking the all sp3 phospholane of (R,R)-Ph-BPE, a highly selective ligand in asymmetric hydroformylation. The reduced bisdiazaphospholane (red-BDP) ligands were shown crystallographically to have an increased C-N-N-C torsion angle - this puckering resembles the structure of (R,R)-Ph-BPE and has a dramatic influence on regioselectivity in rhodium catalyzed hydroformylation. The red-BDPs demonstrated up to a 5-fold increase in selectivity for the branched aldehyde compared to the acylhydrazine parent ligands. This work demonstrates a facile procedure for increased branched selectivity from the highly active and accessible class of BDP ligands in hydroformylation.
Tunable P-Chiral Bisdihydrobenzooxaphosphole Ligands for Enantioselective Hydroformylation
Tan, Renchang,Zheng, Xin,Qu, Bo,Sader, C. Avery,Fandrick, Keith R.,Senanayake, Chris H.,Zhang, Xumu
supporting information, p. 3346 - 3349 (2016/07/26)
Air-stable and tunable chiral bisdihydrobenzooxaphosphole ligands (BIBOPs) were employed in rhodium-catalyzed asymmetric hydroformylation of various terminal olefins with excellent conversions (>99%), moderate-to-excellent enantioselectivities (up to 95:5 er), and branched to linear ratios (b:l) of up to 400.
Easily accessible and highly tunable bisphosphine ligands for asymmetric hydroformylation of terminal and internal alkenes
Xu, Kun,Zheng, Xin,Wang, Zhiyong,Zhang, Xumu
, p. 4357 - 4362 (2014/05/06)
An efficient methodology for synthesizing a small library of easily tunable and sterically bulky ligands for asymmetric hydroformylation (AHF) has been reported. Five groups of alkene substrates have been tested with excellent conversions, moderate-to-excellent regio- and enantioselectivities. Among the best result of the reported literature, application of ligand 1 c in the highly selective AHF of the challenging substrate 2,5-dihydrofuran yielded almost one isomer in up to 99 % conversion along with enantiomeric excesses (ee) of up to 92 %. Highly enantioselective AHF of dihydropyrrole substrates is achieved using the same ligand, with up to 95 % ee and up to >1:50 β-isomer/α- isomer ratio. The simpler the better! An efficient method for the easy and tunable synthesis of a series of asymmetric hydroformylation (AHF) ligands from low-cost, commercially available starting materials has been reported. These ligands can give excellent conversions and moderate to excellent regio- and enantioselectivities for a broad range of mono- and disubstituted alkenes with a low catalyst loading (substrate-to-catalyst ratios (S/C) of 1000:1 to 3000:1).
Immobilized bisdiazaphospholane catalysts for asymmetric hydroformylation
Adint, Tyler T.,Landis, Clark R.
, p. 7943 - 7953 (2014/06/23)
Condensation reactions of enantiopure bis-3,4-diazaphospholanes (BDPs) that are functionalized with carboxylic acids enable covalent attachment to bead and silica supports. Exposure of tethered BDPs to the hydroformylation catalyst precursor, Rh(acac)(CO)2, yields catalysts for immobilized asymmetric hydroformylation (iAHF) of prochiral alkenes. Compared with homogeneous catalysts, catalysts immobilized on Tentagel resins exhibit similarly high regioselectivity and enantioselectivity. When corrected for apparent catalyst loading, the activity of the immobilized catalysts approaches that of the homogeneous analogues. Excellent recyclability with trace levels of rhodium leaching are observed in batch and flow reactor conditions. Silica-bound catalysts exhibit poorer enantioselectivities.
Libraries of bisdiazaphospholanes and optimization of rhodium-catalyzed enantioselective hydroformylation
Adint, Tyler T.,Wong, Gene W.,Landis, Clark R.
, p. 4231 - 4238 (2013/06/05)
Twelve chiral bis-3,4-diazaphospholane ligands and six alkene substrates (styrene, vinyl acetate, allyloxy-tert-butyldimethylsilane, (E)-1-phenyl-1,3- butadiene, 2,3-dihydrofuran, and 2,5-dihydrofuran) probe the influence of steric bulk on the activity and selectivity of asymmetric hydroformylation (AHF) catalysts. Reaction of an enantiopure bisdiazaphospholane tetraacyl fluoride with primary or secondary amines yields a small library of tetracarboxamides. For all six substrates, manipulation of reaction conditions and bisdiazaphospholane ligands enables state-of-the-art performance (90% or higher ee, good regioselectivity, and high turnover rates). For the nondihydrofuran substrates, the previously reported ligand, (S,S)-2, is generally most effective. However, optimal regio- and enantioselective hydroformylation of 2,3-dihydrofuran (up to 3.8:1 α-isomer/β-isomer ratio and 90% ee for the α-isomer) and 2,5-dihydrofuran (up to 1:30 α-isomer/β- isomer ratio and 95% ee for the β-isomer) arises from bisdiazaphospholanes containing tertiary carboxamides. Hydroformylation of either 2,3- or 2,5-dihydrofuran yields some of the β-formyl product. However, the absolute sense of stereochemistry is inverted. A stereoelectronic map rationalizes the opposing enantiopreferences
Diisobutylaluminum hydride reductions revitalized: A fast, robust, and selective continuous flow system for aldehyde synthesis
Webb, Damien,Jamison, Timothy F.
supporting information; experimental part, p. 568 - 571 (2012/03/26)
A continuous flow system for the multiparameter (flow rate, temperature, residence time, stoichiometry) optimization of the DIBALH reduction of esters to aldehydes is described. Incorporating an in-line quench (MeOH), these transformations are generally complete in fewer than 60 s. Mixing of the DIBALH and ester solutions was observed to be an exceptionally critical parameter for optimum results. This system thus provides general guidelines based on the structure of the ester for selective reduction of an ester without overreduction.
Enantioselective hydroformylation of N-vinyl carboxamides, allyl carbamates, and allyl ethers using chiral diazaphospholane ligands
McDonald, Richard I.,Wong, Gene W.,Neupane, Ram P.,Stahl, Shannon S.,Landis, Clark R.
supporting information; experimental part, p. 14027 - 14029 (2011/01/04)
Rhodium complexes of diazaphospholane ligands catalyze the asymmetric hydroformylation of N-vinyl carboxamides, allyl ethers, and allyl carbamates; products include 1,2- and 1,3-aminoaldehydes and 1,3-alkoxyaldehydes. Using glass pressure bottles, short reaction times (generally less than 6 h), and low catalyst loading (commonly 0.5 mol %), 20 substrates are successfully converted to chiral aldehydes with useful regioselectivity and high enantioselectivity (up to 99% ee). Chiral Roche aldehyde is obtained with 97% ee from the hydroformylation of allyl silyl ethers. Commonly difficult substrates such as 1,1- and 1,2-disubstituted alkenes undergo effective hydroformylation with 89-97% ee and complete conversion for six examples. Palladium-catalyzed aerobic oxidative amination of allyl benzyl ether followed by enantioselective hydroformylation yields the β3-aminoaldehyde with 74% ee.
