Zinc Catalyzed and Mediated Propargylations with Propargyl Boronates
摘要:
The utility of allenyl and propargyl boronates for the propargylation of aldehydes and ketones mediated by zinc is presented. The reaction Is catalytic in zinc with allenyl or propargyl borolanes. The propargylation with crystalline and air-stable propargyl diethanolamine boronates was also achieved. A catalytic cycle is proposed, and preliminary mechanistic studies are discussed.
Application of elementoorganic compounds of 15th and 16th Groups in organic synthesis. 100. Reactions of carbonyl compounds with [(trimethylsilyl)propargyl]diisobutyltelluronium bromide mediated by different strong bases: highly regioselective synthesis of (trimethylsilyl)propargyl alcohols and highly stereoselective synthesis of cis-(trimethylsilyl)alkynyl epoxides
摘要:
[(Trimethylsilyl)propargyl)]diisobutyltelluronium bromide (1), after being treated with alkyl- or aryllithium reagent, undergoes a lithium-tellurium exchange reaction via an unstable transient tetraorganyltellurium intermediate, and the in situ generated lithium species reacts with carbonyl compounds to give (trimethylsilyl)propargyl alcohols 2 in high yields with high regioselectivity. However, when the telluronium salt 1 was treated with nonnucleophilic bases such as LDA or lithium 2,2,6,6-tetramethylpiperidide, the moderately stabilized silylated telluronium ylide formed. The silylated telluronium ylide reacted with carbonyl compounds to afford (trimethylsilyl) alkynyl epoxides 11 in good to excellent yields with high cis stereoselectivity.
Regioselective Addition Reactions of Propargyl Bromides to Carbonyl Compounds with Gallium Catalyzed by Indium
作者:Phil Ho Lee、Hyun Kim、Kooyeon Lee
DOI:10.1002/adsc.200505046
日期:2005.7
propargyl bromides having substituents at the γ-position and gallium in the presence of 5 mol % of indium with aldehydes and ketones selectively produced homoallenyl alcohols in good to excellent yields. Treatment of organogallium reagents obtained from propargyl bromide or propargyl bromides having substituents at the α-position and gallium in the presence of 5 mol % of indium with carbonyl compounds selectively
Gallium-mediated highly regioselective reactions of trimethylsilylpropargyl bromide and trimethylsilylallyl bromide with carbonyl compounds
作者:Ying Han、Yao-Zeng Huang
DOI:10.1016/s0040-4039(00)78562-5
日期:1994.12
One-pot reactions of gallium powder, trimethylsilylpropargyl bromide, aldehydes or ketones in the presence of KI and LiCl show very high acetylenic selectivity and under the same conditions, trimethylsilylallyl bromide also exhibits very high selectivity favoring α-adducts.
Selective multiple methylene insertion reactions mediated by iodomethylzine iodide: Mechanistic considerations and synthetic applications
作者:Michael J. Rozema、Paul Knochel
DOI:10.1016/s0040-4039(00)85980-8
日期:1991.4
The reaction of alkynylcoppers 1 with an excess of iodomethylzinc iodide selectively furnishes the quadruple methyleneinsertion copper organometallics 2 in fair to good yields. The mechanism of the reaction has been investigated and postulated intermediates such as 4 or 8 have been trapped with electrophiles like aldehydes or ketones in excellent yields. A new in situ preparation of propargylic copper
Regioselective Propargylation of Carbonyl Compounds with (3-Bromoprop-1-ynyl)trimethylsilane Promoted by Reactive Barium
作者:Akira Yanagisawa、Shogo Okitsu、Takayoshi Arai
DOI:10.1055/s-2005-869874
日期:——
A Barbier-type propargylation of aldehydes with (3-bromoprop-1-ynyl)trimethylsilane has been achieved using reactive barium as a low-valent metal in THF. This process is effective also for obtaining the desired homopropargylic alcohols in high yields from the corresponding ketones including enolizable ketones such as cyclopent-2-enone.