- M -C2B10H11HgCl/AgOTf-Catalyzed Reaction for Reductive Deoxygenation
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A m -C2B10H11HgCl/AgOTf-catalyzed reaction of allyl silyl ethers with N -Boc- N ′-tosylhydrazine has been developed. Under mild conditions, the resulting allyl hydrazine products were transformed into naked alkenes in good yield. Furthermore, the used m -C2B10H11HgCl could be recovered quantitatively.
- Yamasaki, Naoto,Kanno, Marina,Sakamoto, Kyohei,Kasai, Yusuke,Imagawa, Hiroshi,Yamamoto, Hirofumi
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p. 169 - 175
(2018/03/26)
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- Radical chain reduction of alkylboron compounds with catechols
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The conversion of alkylboranes to the corresponding alkanes is classically per-formed via protonolysis of alkylboranes. This simple reaction requires the use of severe reaction conditions, that is, treatment with a carboxylic acid at high temperature (>150 °C). We report here a mild radical procedure for the transformation of organoboranes to alkanes. 4-tert-Butylcatechol, a well-established radical inhibitor and antioxidant, is acting as a source of hydrogen atoms. An efficient chain reaction is observed due to the exceptional reactivity of phenoxyl radicals toward alkylboranes. The reaction has been applied to a wide range of organoboron derivatives such as B- alkylcatecholboranes, trialkylboranes, pinacolboronates, and alkylboronic acids. Furthermore, the so far elusive rate constants for the hydrogen transfer between secondary alkyl radical and catechol derivatives have been experimentally determined. Interestingly, they are less than 1 order of magnitude slower than that of tin hydride at 80 °C, making catechols particularly attractive for a wide range of transformations involving C-C bond formation.
- Villa, Giorgio,Povie, Guillaume,Renaud, Philippe
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p. 5913 - 5920
(2011/06/16)
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- Practical synthesis of optically pure menthylamines starting from racemic neomenthol
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A reliable and scalable route to racemic and highly enantiomerically enriched menthylamines exploits the technical product rac-neomenthol as the starting material. The elaborated protocol is based on nucleophilic substitution of the hydroxy moiety by azide. Subsequent reduction and resolution with tartaric acid provides the desired optically enriched menthylamines.
- Welschoff, Nina,Waldvogel, Siegfried R.
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scheme or table
p. 3596 - 3601
(2010/12/19)
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- O-DPPB-directed copper-mediated and -Catalyzed allylic substitution with grignard reagents
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The ortho-diphenylphosphanylbenzoyl (o-DPPB) group was explored as a directing leaving group in copper-mediated and copper-catalyzed allylic substitution with Grignard reagents. Complete control of chemo-, regio- and stereoselectivity with complete syn-1,3-chirality transfer was observed as a result of the directed nature of the reaction. No excess of or ganometallic reagent is required and the directing group can be recovered quantitatively. Coordination studies in the solid state and in solution have shown that two substrates are bound via the phosphine function of the directing group at copper. Dynamic NMR experiments in solution are in agreement with a ligand-exchange process at copper, a prerequisite for the development of a substoichiometric process.
- Demel, Peter,Keller, Manfred,Breit, Bernhard
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p. 6669 - 6683
(2008/09/16)
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- Fragmentation of menthyl- and neomenthyloxychlorocarbenes: Elimination and substitution reactions of alicyclic oxychlorocarbenes
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Fragmentations of menthyloxychlorocarbene (5) and neomenthyloxychlorocarbene (6) follow distinct pathways to (largely) stereochemically retained substitution products from 5 and elimination products from 6, closely resembling the product distributions from deaminations of the corresponding menthyl- and neomenthylamines.
- Moss, Robert A.,Johnson, Lauren A.,Kacprzynski, Monica,Sauers, Ronald R.
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p. 5114 - 5118
(2007/10/03)
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- Copper-Mediated and -Catalyzed o-DPPB-Directed Allylic Substitution
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Complete control of chemo-, regio- and stereoselectivity in the course of copper-catalyzed and -mediated allylic substitution could be obtained with me ortho-diphenylphosphanyl (o-DPPB) function as a reagent-directing leaving group. Complete chirality transfer by way of a syn-addition process has been achieved for cyclic and acyclic systems. Readily available Grignard reagents may be employed as nucleophiles and the directing o-DPPB group can be recovered quantitatively. The reaction requires neither cooling nor an excess of organometallic reagent.
- Breit, Bernhard,Demel, Peter
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p. 429 - 432
(2007/10/03)
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- Dehydration of secondary alcohols via thermolysis of in situ generated alkyl diphenyl phosphates: An inexpensive and environmentally compatible method for the preparation of alkenes
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Secondary alcohols are converted into diphenyl phosphate esters by the action of triphenyl phosphate or diphenyl phosphorochloridate in high-boiling, water-miscible solvents in the presence of base. The alkyl diphenyl phosphates undergo thermolysis to afford high yields of alkenes which distill from the reaction mixtures. Purification of the products is achieved by extraction with dilute sulfuric acid which removes traces of solvent and base that may have codistilled. The ratios of 2- (14) and 3-menthene (15), obtained from menthol (13) and neomenthol (16), and the formation of rearranged alkenes by 1,2-shifts from 3, 6, and 3,3-dimethylbutan-2-ol are consistent with ionic intermediates of the elimination reaction. The novel dehydration method offers distinct and important advantages over the existing methods.
- Quast,Dietz
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p. 1300 - 1304
(2007/10/02)
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- ALYLATION OF ALLYLIC CYCLOHEXENYL ESTERS WITH TRIALKYLALUMINIUM REAGENTS. A REGIO AND STEREOCHEMICAL STUDY
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Regio and stereochemistry of the title reaction appear to be strongly influenced by the nature of both organometallic and allylic reagents.The results are discussed in view of the intervention of ion-pair intermediates.
- Gallina, C.
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p. 519 - 522
(2007/10/02)
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- REGIO AND STEREOSPECIFIC SYNTHESIS OF CIS AND TRANS 3-METHYL-6-METHYLETHYL CYCLOHEXENES AND 3-METHYL-4-METHYLETHYLCYCLOHEXENES. REACTIONS OF ALLYLIC ACETATES AND CARBAMATES WITH Li2Cu3Me5 AND LiCuMe2
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The isomeric alkenes 1-4 have been obtained by syn, γ substitution of the appropriate allylic carbamates with Li2Cu3Me5.The behaviour of carbamates is deeply affected by the nature of the copper reagent.
- Gallina, C.
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p. 3093 - 3096
(2007/10/02)
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- INVESTIGATION OF COMPOUNDS OF THE MENTHANE SERIES. XVI. REDUCTION OF o- AND p-ISOPROPENYLTOLUENES WITH CALCIUM HEXAAMMONIATE
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In the reduction of o- and p-isopropenyltoluenes with calcium hexaammoniate in the presence of protic and aprotic solvents 1,2-addition of hydrogen mostly occurs with the formation of o- and p-cymenes and o- and p-menthatrienes, which under the reaction conditions give the products from 1,2- and 1,4-addition of hydrogen.
- Bazyl'chik, V. V.
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p. 1847 - 1851
(2007/10/02)
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