154377-45-4

Upstream product

• 873-66-5 1-propenylbenzene 
• 637-50-3 1-phenylpropene 

Downstream Products

• 1565-74-8 (R)-1-phenyl-1-propanol 

Relevant academic research and scientific papers

Exerting control over the helical chirality in the main chain of sergeants-and-soldiers-type poly(quinoxaline-2,3-diyl)s by changing from random to block copolymerization protocols

Chiral random poly(quinoxaline-2,3-diyl) polymers of the sergeants-and-soldiers-type (sergeant units bearing (S)-3-octyloxymethyl groups) adopt an M- or P-helical conformation in the presence of achiral units bearing propoxymethyl or butoxy groups (soldier units), respectively. Unusual bidirectional induction of the helical sense can be observed for a copolymer with butoxy soldier units upon changing the mole fraction of the sergeant units. In the presence of 16-20% of sergeant units, the selective induction of a P-helix was observed, while the selective induction of an M-helix was observed for a mole fraction of sergeant units of more than 60%. This phenomenon could be successfully employed to control the helical chirality of copolymers by applying either random or block copolymerization protocols. Random or block copolymerization of sergeant and soldier monomers in a 18:82 ratio resulted in the formation of 250mers with almost absolute P- or M-helical conformation, respectively (>99% ee). Incorporation of a small amount of coordination sites into the random and block copolymers resulted in chiral macromolecular ligands, which allowed the enantioselective synthesis of both enantiomers in the Pd-catalyzed asymmetric hydrosilylation of β-methylstyrene.

Facile preparation of poly(quinoxaline-2,3-diyl)s via aromatizing polymerization of 1,2-diisocyanobenzenes using phosphine complexes of nickel(II) salts

Polymerizations of 1,2-diisocyanobenzenes to afford poly-(quinoxaline-2,3-diyl)s were investigated in the presence of various metal salts and their phosphine complexes, whereby especially the stable and easily-accessible [NiCl2(PMe3)2] was found to exhibit a high polymerization activity. The end groups of the resulting polymers were determined by mass spectrometry measurements as-P+Me3 and -H, indicative of a nucleophilic attack of PMe3 towards an isocyano group as the initial step of the polymerization. A chiral polymer ligand, prepared by such a [NiCl2(PMe3)2]-mediated polymerization, demonstrated high enantioselectivities in palladium-catalyzed asymmetric hydrosilylation reactions, suggesting that the polymeric catalyst adopted a single-handed helical backbone.

Majority-Rules-Type Helical Poly(quinoxaline-2,3-diyl)s as Highly Efficient Chirality-Amplification Systems for Asymmetric Catalysis

A highly efficient majority-rules effect of poly(quinoxaline-2,3-diyl)s (PQXs) bearing 2-butoxymethyl chiral side chains at the 6- and 7-positions was established and attributed to large ΔGh values (0.22-0.41 kJmol-1), which are defined as the energy difference between P- and M-helical conformations per chiral unit. A PQX copolymer prepared from a monomer derived from (R)-2-octanol (23% ee) and a monomer bearing a PPh2 group adopted a single-handed helical structure (>99%) and could be used as a highly enantioselective chiral ligand in palladium-catalyzed asymmetric reactions (products formed with up to 94% ee), in which the enantioselectivity could be switched by solvent-dependent inversion of the helical PQX backbone. Bowing to the majority: Poly(quinoxaline-2,3-diyl) containing PPh2 groups and chiral side chains derived from (R)-2-octanol with 23% ee exhibited a single-handed-helical conformation and served as a highly enantioselective chiral ligand in palladium-catalyzed reactions (see scheme; se=screw-sense excess). The chirality of the polymer could be switched by a solvent effect to enable the synthesis of the enantiomeric products.

Asymmetric palladium-catalyzed hydrosilylation of styrenes using efficient chiral spiro phosphoramidite ligands

Asymmetric hydrosilylation of styrene derivatives with trichlorosilane in the presence of palladium complexes of chiral spiro phosphoramidites provided 1-aryl-1-silylalkanes as single regioisomers in high yields, which have been oxidized with hydrogen peroxide to give the corresponding chiral alcohols in up to 99.1% ee.

Highly enantioselective hydrosilylation of aromatic alkenes

Currently, the most effective and economic way to convert an alkene into an optically active alcohol is the two-step sequence: hydrosilylation/oxidation. Much work has been devoted to elucidating effective catalysts for this process, but hitherto only one effective and highly stereoselective process has been available. Herein we present a novel catalytic system for the asymmetric hydrosilylation of aromatic alkenes, giving the products in high yields and with the highest enantioselectivity (up to 99% ee) ever observed for this reaction. The reaction works efficiently for a variety of substituted aromatic alkenes, giving access after Tamao oxidation to almost optically pure benzylic alcohols in high yields. Copyright

Asymmetric hydrosilylation of styrenes catalyzed by palladium-MOP complexes: Ligand modification and mechanistic studies

In the palladium-catalyzed asymmetric hydrosilylation of styrene (3a) with trichlorosilane, several chiral monophosphine ligands, (R)-2-diarylphosphino-1,1′-binaphthyls (2a-g), were examined for their enantioselectivity. The highest enantioselectivity was observed in the reaction with (R)-2-bis[3,5-bis(trifluoromethyl)phenyl]phosphino-1, 1′-binaphthyl (2g), which gave (S)-1-phenylethanol (5a) of 98% ee after oxidation of the hydrosilylation product, 1-phenyl-1-(trichlorosilyl)ethane (4a). The palladium complex of 2g also efficiently catalyzed the asymmetric hydrosilylation of substituted styrenes on the phenyl ring or at the β position to give the corresponding chiral benzylic alcohols of over 96% ee. Deuterium-labeling studies on the hydrosilylation of regiospecifically deuterated styrene revealed that β-hydrogen elimination from 1-phenylethyl(silyl)palladium intermediate is very fast compared with reductive elimination giving hydrosilylation product when ligand 2g is used. The reaction of o-allylstyrene (9) with trichlorosilane catalyzed by (R)-2g/Pd gave (1S,2R)-1-methyl-2-(trichlorosilylmethyl)indan (10) (91% ee) and (S)-1-(2-(propenyl)phenyl)-1-trichlorosilylethanes (11a and 11b) (95% ee). On the basis of their opposite configurations at the benzylic position, a rationale for the high enantioselectivity of ligand 2g is proposed.

Palladium-catalysed Asymmetric Hydrosilylation of Styrenes with a New Chiral Monodentate Phosphine Ligand

Asymmetric hydrosilylation of styrenes (ArCH=CHR) with trichlorosilane in the presence of a palladium catalyst (0.1 molpercent) bearing a new chiral monodentate phosphine ligand, (S)-2-diphenylphosphino-1,1'-binaphthyl , followed by oxidation of the resulting 1-aryl-1-silylalkanes, gives optically active benzylic alcohols of up to 96percent enantiomeric excess (e.e.).

Regio- and Enantioselective Hydrosilylation of 1-Arylalkenes by Use of Palladium-MOP Catalyst

Hydrosilylation of styrenes bearing β-substituents with trichlorosilane was catalyzed by a palladium complex (0.1 mol percent) coordinated with (R)-2-methoxy-2'-diphenylphosphino-1,1'-binaphthyl ((R)-MeO-MOP) to give high yields of optically active 1-aryl-1-silylalkanes (80-85percent ee) as single regioisomers.The resulting silanes were readily converted into the corresponding optically active alcohols (80-99percent yield).