Libraries of bisdiazaphospholanes and optimization of rhodium-catalyzed enantioselective hydroformylation.

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/ß-isomer ratio and 90% ee for the α-isomer) and 2,5-dihydrofuran (up to <1:30 α-isomer/ß-isomer ratio and 95% ee for the ß-isomer) arises from bisdiazaphospholanes containing tertiary carboxamides. Hydroformylation of either 2,3- or 2,5-dihydrofuran yields some of the ß-formyl product. However, the absolute sense of stereochemistry is inverted. A stereoelectronic map rationalizes the opposing enantiopreferences.

Enantioselective hydroformylation of N-vinyl carboxamides, allyl carbamates, and allyl ethers using chiral diazaphospholane ligands.

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 ß(3)-aminoaldehyde with 74% ee.

Insertion of CO2, ketones, and aldehydes into the C-Li bond of 1,3,5-triaza-7-phosphaadamantan-6-yllithium.

The synthesis and structures of a series of new water-soluble phosphine ligands based on 1,3,5-triaza-7-phosphaadamantane (PTA) are described. Insertion of aldehydes or ketones into the C-Li bond of 1,3,5-triaza-7-phosphaadamantan-6-yllithium (PTA-Li) resulted in the formation of a series of slightly water-soluble beta-phosphino alcohols (PTA-CRR'OH, R = C6H5, C(6)H(4)OCH(3), ferrocenyl; R' = H, C(6)H(5), C(6)H(4)OCH(3)) derived from the heterocyclic phosphine PTA. Insertion of CO(2) yielded the highly water-soluble carboxylate PTA-CO(2)Li, S(2)5 degrees approximately 800 g/L. The compounds have been fully characterized in the solid state by X-ray crystallography and in solution by multinuclear NMR spectroscopy. The addition of PTA-Li to symmetric ketones results in a racemic mixture of PTA-CR(2)OH ligands with a single resonance in the (31)P{(1)H} NMR spectrum between -95 and -97 ppm. The addition of PTA-Li to aldehydes results in a mixture of diasteromeric compounds, PTA-CHROH, with two (31)P{(1)H} NMR resonances between -100 and -106 ppm. Three (eta(6)-arene)RuCl(2)(PTA-CRR'OH) complexes of these ligands were synthesized and characterized, with the ligands binding in a kappa1 coordination mode. All the ligands and ruthenium complexes are slightly soluble in water with S25 degrees = 3.9-11.1 g/L for the PTA-CRR'OH ligands and S(25) degrees = 3.3-14.1 g/L for the (eta(6)-arene)RuCl(2)(PTA-CRR'OH) complexes.

Synthesis and coordination chemistry of a novel bidentate phosphine: 6-(diphenylphosphino)-1,3,5-triaza-7-phosphaadamantane (PTA-PPh2).

The upper rim of 1,3,5-triaza-7-phosphaadamantane (PTA) has been modified for the first time. Lithiation of PTA, with n-butyllithium, resulted in deprotonation of an alpha-phosphorus methylene and the formation of 1,3,5-triaza-7-phosphaadamantane-6-yllithium (PTA-Li). The chiral chelating phosphine 6-(diphenylphosphino)-1,3,5-triaza-7-phosphaadamantane (PTA-PPh2) was synthesized, in racemic form, by the reaction of PTA-Li with ClPPh2. PTA-PPh2 has been fully characterized in solution by multinuclear NMR spectroscopy and mass spectrometry and in the solid state by X-ray crystallography. The 31P NMR spectrum contains a pair of doublets at -19.8 and -100.1 ppm (d, (2)J(PP) = 65 Hz). Unlike PTA, the new bidentate phosphine, PTA-PPh2, is insoluble in aqueous solutions. Two group 6 metal carbonyl complexes, [M(CO)4(PTA-PPh2)] (M = W and Mo), were synthesized by the addition of PTA-PPh2 to cis-[M(CO)4(pip)2] and characterized by NMR spectroscopy, IR spectroscopy, and X-ray crystallography. Also reported are the solid-state structures of cis-[W(CO)4PTA2], cis-[W(CO)4(PTA)(PPh3)], and [W(CO)4DPPM] (DPPM = diphenylphosphinomethane). PTA-PPh2 appears to be sterically similar to and slightly more electron-donating than DPPM.