ISSN:0021-2148    

DOI:10.1002/ijch.198400010

出版商:WILEY‐VCH Verlag    

年代:1984

数据来源: WILEY

摘要:

AbstractMethallylphenyl sulfide2undergoes trimetalation on treatment with n‐butyllithium and TMEDA. The trilithiated product gives with chlorotrimethylsilane the trisilyl derivative3. A similar reaction of the tertiary amine4leads to a mixture of the trisilyl7and two disilyl derivatives5and

ISSN:0021-2148    

DOI:10.1002/ijch.198400011

出版商:WILEY‐VCH Verlag    

年代:1984

数据来源: WILEY

摘要:

AbstractThexylchloroborane‐dimethyl sulfide (1) hydroborates representative 1‐bromo‐1‐alkynes in the presence of 10% boron tribromide as a catalyst to afford thexyl‐(cis‐1‐bromo‐1‐alkenyl)‐chloroboranes (2). Treatment of these intermediates with isopropyl alcohol provides the corresponding isopropyl thexyl(cis‐1‐bromo‐1‐alkenyl)borinates (3B). Subsequent treatment with alkynyllithium gives the corresponding “ate” complexes (4) which undergo intramolecular migration of the alkynyl group from boron to the adjacent carbon, displacing the bromine, producing the correspondingcis‐vinylboranes (5). These intermediates (5) provide the corresponding alkynyl ketones (6) on oxidation and the corresponding stereodefined conjugated enynes (7) of high isomeric purity on protonolysis. Yields in

ISSN:0021-2148    

DOI:10.1002/ijch.198400012

出版商:WILEY‐VCH Verlag    

年代:1984

数据来源: WILEY

摘要:

AbstractThe reaction of 6‐trimethylsilylhex‐1‐en‐5‐yne withi‐Bu3Al (1.1 equivalents) and a catalytic amount of Cl2ZrCp2in 1,2‐dichloroethane or CH2Cl2at room temperature produces, after protonolysis, trimethylsilylmethylenecyclopentane in 85% yield. Upon iodinolysis of the reaction mixture, the corresponding iodide is obtained in 68% yield. Under the same reaction conditions, 7‐trimethylsilylhept‐1‐en‐6‐yne is converted into trimethylsilylmethylenecyclohexane in 72% yield upon protonolysis of the reaction mixture. Attempts to produce four‐ or seven‐membered ring compounds have not been successful. Thei‐Bu3Al–Cl2ZrCp2reaction of 6‐trimethylsilyl‐4‐methylhex‐1‐en‐5‐yne is nonstereoselective. However, the use of I2ZrCp2in place of Cl2ZrCp2improves theE/Zratio to ca 80/20. The reaction of 1‐trimethylsilylhex‐5‐en‐1‐yn‐3‐ol withi‐Bu3Al–Cl2ZrCp2gives the ca 90% pureZisomer under “kinetic” conditions and the ca 97%E

ISSN:0021-2148    

DOI:10.1002/ijch.198400013

出版商:WILEY‐VCH Verlag    

年代:1984

数据来源: WILEY

摘要:

AbstractNovel reducing systems, comprising various silicon hydrides and a soluble palladium(0) catalyst, allow very mild and chemoselective reductive cleavage of allylic heterosubstituents. Other easily‐reducible functionalities such as ketones, aldehydes and Michael‐acceptors are not affected under these conditions. The relative reactivities of twelve commercially available silanes towards allylic reduction were determined using1H NMR techniques. Similarly, the role of various reaction parameters such as temperature, solvent and concentration of reactants, and the effect of added water and zinc chloride on the reduction rate have been stud

ISSN:0021-2148    

DOI:10.1002/ijch.198400014

出版商:WILEY‐VCH Verlag    

年代:1984

数据来源: WILEY

摘要:

AbstractFour different (R)‐3‐substituted cyclohexanones of 65–96% enantiomeric purity have been prepared in 58–84% yields via organometallic conjugate additions to (S)‐2‐(p‐tolylsulfinyl)cyclohexenone in 2,5‐dimethyltetrahydrofuran (DMTHF) as a solvent which allows more effective metal ion chelation by the bidentate β‐ketosulfoxide (and therefore higher asymmetric induction) than does THF. Several recently‐reported organotitanium reagents have been used effectively for the first ti

ISSN:0021-2148    

DOI:10.1002/ijch.198400015

出版商:WILEY‐VCH Verlag    

年代:1984

数据来源: WILEY

摘要:

AbstractReaction of tricarbonylcycloheptatrienemanganese hexafluorophosphate with a wide range of enolate nucleophiles derived from malonic esters, phenylsulfonylesters, β‐ketoesters and cyclohexanones proceeds cleanly to give 6‐substituted tricarbonyl(1–5‐η‐cycloheptadienyl)manganese complexes3. It was found that demetallation with concomitant stereospecific hydroxylation, to give substituted cycloheptadienes, could be accomplished by direct treatment of the dienyl complexes with ceric ammonium nitrate in buffered wet acetone. Complexes3a–3cgave mixtures of hydroxy esters and gamma lactones6and7in proportions which depended on the nature of the substituent present. A novel and potentially useful demetallative cyclofunctionalization was found to occur on treatment of hydroxy ester3mwith excess iodine in acetonitrile, to give the cyclic ether10as the only obser

ISSN:0021-2148    

DOI:10.1002/ijch.198400016

出版商:WILEY‐VCH Verlag    

年代:1984

数据来源: WILEY

摘要:

AbstractThe organoiron complex4is readily prepared from α‐bromopyruvic ester diethyl acetal, and has been shown to serve as an effective α‐acrylic ester cation equivalent, in the synthesis of α‐methylene‐γ‐lactones. Cyclohexanone lithium enolate is transformed to either thecisortransfused lactones12c, t, and ethyl acetoacetate lithium enolate can be converted to the lactone21t. The use of methyl 3‐oxohexadecanoate as starting material provides a stereospecific synthesis of protolichesterinic ac

ISSN:0021-2148    

DOI:10.1002/ijch.198400017

出版商:WILEY‐VCH Verlag    

年代:1984

数据来源: WILEY

摘要:

AbstractThe regiospecific alkylation of cyclic ketones and TMS enol ethers by the cobalt‐stabilized propargyl cations1followed by demetalation and regiospecific acetylene hydration proceeds in good overall yield to produce 1,4‐diketones. The latter are efficiently cyclized in the presence of base to annelated cyclopenteno

ISSN:0021-2148    

DOI:10.1002/ijch.198400018

出版商:WILEY‐VCH Verlag    

年代:1984

数据来源: WILEY

摘要:

AbstractMethylmagnesium bromide adds to trimethylsilyloctyne (1) in the presence of 10 mol% 1:0.67 nickel acetylacetonate‐trimethylaluminum to give a 9:1 mixture of alkenyl Grignard reagents2aand3a. This mixture reacts with water, deuterium oxide, formaldehyde, acetaldehyde, carbon dioxide, iodine, vinyl bromide or allyl bromide to give the expected products2, 3bto2, 3j. Nickel catalyzed carbometallation of4with MeMgBr followed by quenching with formaldehyde and desilylation givestrans, trans‐farnesol (5c). Nickel catalyzed addition of MeMgBr to6aand6bproceeds analogously, except that initially formed alkenyl Grignard reagents7aand7bisomerize completely to8aand8bwhich are stabilized by chelation. This carbometallation reaction allows the synthesis of both isomers of an allylic alcohol, such as12and13, from a common intermediat

ISSN:0021-2148    

DOI:10.1002/ijch.198400019

出版商:WILEY‐VCH Verlag    

年代:1984

数据来源: WILEY