Synthesis of .gamma.- and .delta.-lactones by free-radical annelation of Se-phenyl selenocarbonates
摘要:
A general method for the synthesis of gamma- and delta-lactones through the intramolecular addition of alkoxycarbonyl radicals, formed by reaction of Se-phenylselenocarbonates with n-Bu3SnH, onto carbon-carbon multiple bonds is described. This free-radical cyclization is characterized by high regioselectivity favoring exo addition and by a high ratio of cyclization to reduction. Monocyclic, fused bicyclic, and spirocyclic lactones are formed in good to excellent yield. Use of allyltri-n-butyltin as a chain-transfer agent in the place of n-Bu3SnH affords the corresponding 3-butenyl lactones.
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.
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.
γ-butyrolactones are obtained in good yields from 4-trimethylsilyl-3-alkyn-1-ols via Wacker-type oxidation reaction. A mechanism is proposed for this transformation: it involves two successive trans-hydroxypalladations followed by a [PdXSiMe3] syn-elimination and explains why the presence of the silyl group is essential in such a process.
Silanes in organic syuthesis. 11. Regiocontrolled synthesis of α-hydroxymethylated (trimethylsilyl)allenes
作者:Rhys G. Daniels、Leo A. Paquette
DOI:10.1016/s0040-4039(01)90382-x
日期:1981.1
The organometallic produced by reaction of trimethylsilylpropargyl bromide with aluminum amalgam in anhydrous tetrahydrofuran condenses readily with aldehydes and ketones to give allenic alcohols resulting from coupling α to the trimethylsilyl substituent.
Synthesis of 3-silyl-2(5 H )-furanone by rhodium-catalyzed cyclocarbonylation
作者:Yukimasa Fukuta、Isamu Matsuda、Kenji Itoh
DOI:10.1016/s0040-4039(00)02234-6
日期:2001.2
of propargyl alcohol derivatives bearing a trialkylsilyl group on the terminal sp-carbon underhydroformylationconditions. The following two requirements must be satisfied for the success of this protocol; (i) the presence of a silyl group on the sp-carbon, and (ii) the presence of a catalytic amount of Rh4(CO)12.
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