- Au-Catalyzed Intermolecular [2+2] Cycloadditions between Chloroalkynes and Unactivated Alkenes
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The [2+2] cycloaddition is a versatile strategy for the synthesis of strained cyclobutenes of high synthetic value. In this study, two efficient intermolecular [2+2] cycloadditions between two different types of chloroalkynes and unactivated alkene are realized with gold catalysis. Of significance is that the reaction works with challenging monosubstituted unactivated alkenes, which is unprecedented in gold catalysis and scarcely documented in other metal-catalyzed/promoted reactions; moreover, the reaction exhibits excellent regioselectivities, which are much better than those reported in literature. With 1,2-disubstituted unactivated alkenes, the reaction is largely stereospecific. The cyclobutene products can be prepared in nearly gram scale and readily undergo further reactions including various cross-coupling reactions using the C(sp2)-Cl and/or C(sp2)-SPh bond, which in turn substantially broaden the scope of accessible cyclobutenes and enhance the synthetic utility of this bimolecular reaction.
- Bai, Yu-Bin,Luo, Zaigang,Wang, Yuguang,Gao, Jin-Ming,Zhang, Liming
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supporting information
p. 5860 - 5865
(2018/05/14)
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- Vinylic Organoboranes. 4. A General, One-Pot Synthesis of 6- and 7-Alkyn-1-ols via Boracyclanes. Influence of Steric Effects in the Iodination of Lithium Alkynyl "Ate" Complexes of Dialkylborinates
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The iodination of the "ate" complexes derived from various B-alkoxyborinane derivatives and 1-alkynyllithium has been investigated.The results indicate the ate complex from B-methoxyborinane is converted into desired 6-alkyn-1-ol in a yield of only 22percent, with much larger amounts, 65percent, of the undesired 1-iodo-1-alkyne.Increases in the steric bulk of the alkoxy group on boron increase the yield of the required 6-alkyn-1-ol with the best results realized with B-(triphenylmethoxy)borinane.Treatment of B-(triphenylmethoxy)borinane with 1-alkynyllithium affords the corresponding "ate" complex.Subsequent iodination induces the migration of one end of the cycloalkyl chain from boron to the adjacent carbon, resulting in the formation of the one-carbon homologated borepane moiety.This then undergoes a rapid deiodoboronation to afford the corresponding (6-alkyn-1-yl)boronate ester.Oxidation of these esters produces the desired 6-alkyn-1-ols in excellent yields (85percent).An attempt to extend this reaction to di-n-alkylborinates to prepare the corresponding unsymmetrical alkynes did not achieve satisfactory results.Alternatively, the iodination of the "ate" complex from B-methylborinane and 1-alkynyllithium, followed by oxidation, provides the required 6-alkyn-1-ols in high yields.This procedure has been successfully extended to the seven-membered borepane moiety to provide the corresponding 7-alkyn-1-ols.Extension of this reaction to the di-n-alkylmethylboranes provides the corresponding unsymmetrical alkynes in good yields.Thus, these procedures constitute a simple, general and one-pot synthesis of the desired alkyn-1-ols, valuable synthons in organic synthesis.Insect pheromones, (Z)-7-tetradecenaland (Z)-7-hexadecenal, were readily prepared in excellent yields by utilizing this convenient procedure.
- Brown, Herbert C.,Basavaiah, D.,Bhat, N. G.
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p. 4518 - 4521
(2007/10/02)
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- Dehydrosilylation of Alkenylsilanes Utilizing Polyvalent Organoiodine Compounds
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Alkenylsilanes, on treatment with iodosylbenzene activated by co-ordination of boron trifluoride-diethyl ether to the oxygen atom, give the corresponding alkynes in good to excellent yields, presumably via vinyliodine(III) intermediates.
- Ochiai, Masahito,Sumi, Kenzo,Nagao, Yoshimitsu,Fujita, Eiichi,Arimoto, Masao,Yamaguchi, Hideo
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p. 697 - 699
(2007/10/02)
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- Long Chain Phenols. Part 17. The Synthesis of 5-resorcinol, 'Cardol monoene,' and of 5-resorcinol Dimethyl Ether, 'Cardol diene' Dimethyl Ether
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Two unsaturated compounds in the 'cardol' series, an important component phenol from Anacardium Occidentale, have been synthesised. 3,5-Dimethoxybenzaldehyde interacted with OH-protected 6-chlorohexan-1-ol in the presence of lithium to give, after acidic treatment, 1-(3,5-dimethoxyphenyl)heptane-1,7-diol which was hydrogenolysed selectively to 7-(3,5-dimethoxyphenyl)heptan-1-ol.Conversion into the bromide and alkylation of lithio-oct-1-yne gave 5-(pentadec-8-ynyl)resorcinol dimethyl ether which was selectively converted into the 8-(Z)-alkene.Dmethylation with lithium iodide gave 5-resorcinol which was identical to 'cardol monoene'.Reaction of 7-(3,5-dimethoxyphenyl)heptyl bromide with lithium derivative of OH-protected propargyl alcohol, gave after acidic treatment 10-(3,5-dimethoxyphenyl)dec-2-yn-1-ol, the bromide of which with pent-1-ynylmagnesium bromide afforded 5-pentadec-8,11-diynylresorcinol dimethyl ether.Selective hydrogenation yielded 5-resorcinol dimethyl ether identical with the dimethyl ether of 'cardol diene.'
- Baylis, Christopher J.,Odle, Stanley W.,Tyman, John H. P.
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p. 132 - 141
(2007/10/02)
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