Titanium Alkoxide-Based Method for Stereoselective Synthesis of Functionalized Conjugated Dienes
作者:Takashi Hamada、Daisuke Suzuki、Hirokazu Urabe、Fumie Sato
DOI:10.1021/ja9905694
日期:1999.8.1
hydrolysis, deuteriolysis, or iodinolysis, gave diene 8, or its bis-deuterated (>99% d2) and bis-iodinated counterparts (9 and 10), in good yields and with high selectivities. This reaction is applicable to the cross-coupling reaction of functionalized acetylenes such as 2-alkynoates and 2-alkynamides 12−18 and a variety of terminal acetylenes 24−28 to give dienes 36−50 in good yields. A terminal acetylene
olefinic stereo-, and diastereoselective addition to aldehydes to give virtually single allyl alcohols. Alternatively, inter- or intramolecular coupling reaction between N-(1-alkynyl)sulfonamides and another acetylene or olefin with the above titanium alkoxide reagent generated the corresponding titanacycles, hydrolysis of which furnished stereo-defined (sulfonylamino)dienes or cyclic compounds.
Concise and Stereoselective Synthesis of Enamides and Dienamides by a Titanium-Mediated Coupling Method
作者:Ryoichi Tanaka、Shuji Hirano、Hirokazu Urabe、Fumie Sato
DOI:10.1021/ol027209x
日期:2003.1.1
Ynamide-titanium alkoxide complexes underwent hydrolysis or addition to aldehydes and ketones to give single, stereodefined di- or trisubstituted enamides in good yields. Alternatively, coupling of a variety of alkyne-titanium alkoxide complexes with terminal ynamides generated amino-substituted titanacyclopentadienes, hydrolysis or aldehyde addition of which afforded stereodefined dienamides.
Phosphine−Substrate Recognition through the C−H···O Hydrogen Bond: Application to the Asymmetric Pauson−Khand Reaction
作者:Jordi Solà、Antoni Riera、Xavier Verdaguer、Miguel A. Maestro
DOI:10.1021/ja053653u
日期:2005.10.1
A unique methine moiety attached to three heteroatoms (0, P, S) and contained in the PuPHOS and CamPHOS ligands serves as a strong hydrogen-bond donor. Nonclassical hydrogen bonding of this methine with an amido-carbonyl acceptor provides a completely diastereoselective ligand exchange process between an alkyne dicobalthexacarbonyl complex and a phosphine ligand. This weak contact has been studied by means of X-ray analysis, H-1 NMR, and quantum mechanical calculations and revealed that the present interaction falls in the range of strong C-(HO)-O-...= C bonds. The hydrogen-bond bias obtained in the ligand exchange process has been exploited in the asymmetric intermolecular Pauson-Khand reaction to yield the corresponding cyclization adducts in up to 94% ee.
Reactions of dialkylamides of trimethylsilylpropiolic acid with triethylgermyllithium
作者:D. A. Bravo-Zhivotovskii、S. D. Pigarev、O. A. Vyazankina、A. S. Medvedeva、L. P. Safronova、N. S. Vyazankin