摘要 :
Except for the catalyst and the temperature, the nature of the solvent also affects the aldol condensation, favouring alpha,beta-unsaturated carbonyl compounds in alcoholic solvents or beta-hydroxyl carbonyl compounds in tetrahydr...
展开
Except for the catalyst and the temperature, the nature of the solvent also affects the aldol condensation, favouring alpha,beta-unsaturated carbonyl compounds in alcoholic solvents or beta-hydroxyl carbonyl compounds in tetrahydrofuran. [References: 7]
收起
摘要 :
The hydrosilylation of aldehydes and ketones under mild conditions with hydrido thiophenolato iron(II) complexes [cis-Fe(H)(SAr)(PMe3)(4)] (1-4) as catalysts is reported using (EtO)(3)SiH as an efficient reducing agent in the yiel...
展开
The hydrosilylation of aldehydes and ketones under mild conditions with hydrido thiophenolato iron(II) complexes [cis-Fe(H)(SAr)(PMe3)(4)] (1-4) as catalysts is reported using (EtO)(3)SiH as an efficient reducing agent in the yields up to 95%. Among them complex 1 is the best catalyst. Complex 1 could also be used as catalyst to reduce the alpha,beta-unsaturated carbonyl compounds selectively to the alpha,beta-unsaturatedalcohols in high yields. (C) 2017 Published by Elsevier B.V.
收起
摘要 :
Roth C9 epimers of Delta(7)-THC (3 and 4) have been synthesized from Delta(8)-THC methyl ether (12). Hydroboration of 12 gave a mixture of stereoisomeric 8-hydroxyhexahydrocannabinols. The 8 alpha-ol was converted into the 9 beta-...
展开
Roth C9 epimers of Delta(7)-THC (3 and 4) have been synthesized from Delta(8)-THC methyl ether (12). Hydroboration of 12 gave a mixture of stereoisomeric 8-hydroxyhexahydrocannabinols. The 8 alpha-ol was converted into the 9 beta-methyl epimer (4) of Delta(7)-THC, while the 8 beta-ol was converted into 3. Molecular modeling indicated that 4 should have significant cannabinoid activity, while 3 was predicted to he weakly active. These predictions were borne out by both in vitro and in vivo pharmacology. [References: 33]
收起
摘要 :
Arylaidehydes can coordinate to nickel(0) in eta(2)-fashion to give eta(2)-arylaldehydenickel complexes. which react with Me3SiOTf or Me3SiCl to give eta(1):eta(1)-siloxybenzylnickel or eta(3)-siloxybenzyl complex. In the presence...
展开
Arylaidehydes can coordinate to nickel(0) in eta(2)-fashion to give eta(2)-arylaldehydenickel complexes. which react with Me3SiOTf or Me3SiCl to give eta(1):eta(1)-siloxybenzylnickel or eta(3)-siloxybenzyl complex. In the presence of PCy3 or CO. Tj I:Tll-siloxvbenzvlnickel complex underwent homocoupling reaction to give a pinacol type product. In the presence of zinc dust. the reductive homocoupling reaction of arylaldehyde proceeded catalytically to form pinacol derivatives in 70-99% yield. On the other hand, eta(3)-siloxybenzylnickel complex regenerated benzaldehyde and Me3SiOTf under a carbon monoxide pressure. (c) 2006 Elsevier Ltd. All rights reserved.
收起
摘要 :
The Pd-catalyzed cross coupling of either #alpha#-haloenones with organometals or #alpha#-metalloenones with organic halides in intrinsically more problematical than the corresponding reaction of #beta#-substituted enones or ordin...
展开
The Pd-catalyzed cross coupling of either #alpha#-haloenones with organometals or #alpha#-metalloenones with organic halides in intrinsically more problematical than the corresponding reaction of #beta#-substituted enones or ordinary alkenyl derivatives. Nonetheless, satisfactory procedures have been developed for cross coupling with organometals containing Zn, Sn, B and Cu to give #alpha#-organylenones in high yields. As in the other cases, organozincs generally display the highest reactivity. In highly demanding and/or delicate situations, some indirect protocols involving protection of carbonyl groups or their temporary reduction help overcome difficulties encountered in direct #alpha#-substitution. Conjugate reduction and conjugate addition of #alpha#-substituted enones provide the corresponding saturated carbonyl compounds in completely regiocontrolled manner. Together with the ability to accommodate unsaturated organic groups, such as aryl, alkenyl, and alkynyl, the new Pd-catalyzed #alpha#-substitution protocols developed since 1987 promise to become synthetic tools of widespread application.
收起
摘要 :
The selective introduction of a boron unit in an organic framework opens new perspectives in both building block design and functionalization protocols. The presence of carbonyl or imino groups in β position with regard to the bo...
展开
The selective introduction of a boron unit in an organic framework opens new perspectives in both building block design and functionalization protocols. The presence of carbonyl or imino groups in β position with regard to the boryl moiety makes them suitable organoboron intermediates for difunctionalized purposes. Catalytic synthetic methodologies have recently been developed to introduce a boryl group at the β - position of α,β-unsaturated esters, ketones, aldehydes, amides, nitriles, as well as imines and oximes. The asymmetric version favours the chiral C_β-B formation which can be eventually transformed into useful alcohols or acetyl functional groups. Alternatively, β-boronate carbonyl or imino compounds can be prepared via alkylation of an enolate with α-haloboronates esters. The subsequent route for the preparation of the chiral β-boronate derivatives required transesterification protocols that successfully provided a series of β-oximo boronates, β-imino boronates and β-carbonyl boronates, with chiral boryl units. This review will enable the reader to understand catalytic and non-catalytic routes for the synthesis of β-boronate carbonyl and imino compounds. The overall mechanistic insights and the perceptible influence of additives on these different synthetic processes, will be discussed. More emphasis will be placed on further applications of the β-boronate compounds in the synthesis of diols or aminoalcohols, in particular where β-chiral centres efficiently control further enantioselective transformation, despite their remote position.
收起
摘要 :
Ketobutenolide 3, easily obtained from santonin (1), has been transformed into two natural furanoeudesmanes 4 and 5, isolated from Commiphora molmol and Tubipora musica, respectively. trans- And cis-decalin systems were obtained b...
展开
Ketobutenolide 3, easily obtained from santonin (1), has been transformed into two natural furanoeudesmanes 4 and 5, isolated from Commiphora molmol and Tubipora musica, respectively. trans- And cis-decalin systems were obtained by stereoselective reduction of the C-4-C-5 double bond in 3 in the following way: hydrogenation of 3 over Pd/C followed by acidic treatment gave the cis isomer 10 as the major product; selective hydrogenation of the C-1-C-2 double bond with the Wilkinson's catalyst followed by reduction with NaTeH yielded mainly the trans isomer 9. Compounds 9 and 10 were transformed into 4 and 5 in parallel sequences. Optical rotation and CD measurements of the synthetic products revealed that the stereochemistry of both natural products should be revised to their enantiomeric form. [References: 41]
收起
摘要 :
A new one-pot room-temperature palladium-catalyzed synthesis of 7-aryltetralones was discovered. This tandem process includes a palladium-catalyzed gamma-selective arylation of the enone 4 followed by a dehydrogenation-aromatizati...
展开
A new one-pot room-temperature palladium-catalyzed synthesis of 7-aryltetralones was discovered. This tandem process includes a palladium-catalyzed gamma-selective arylation of the enone 4 followed by a dehydrogenation-aromatization of the initial cross-coupling product.
收起
摘要 :
Reaction of delta-(sulfonyl)amino-alpha-epoxy ketones with dimethylhydrazine results in cyclization to pyrrolidine-fused beta-hydroxy dimethylhydrazones. elimination affords dihydropyrroles which can be converted to sulfonyl-prote...
展开
Reaction of delta-(sulfonyl)amino-alpha-epoxy ketones with dimethylhydrazine results in cyclization to pyrrolidine-fused beta-hydroxy dimethylhydrazones. elimination affords dihydropyrroles which can be converted to sulfonyl-protected ketopyrroles via oxidation with NIS; alternatively, treatment with DBU affords N-H bearing ketopyrroles. Copyright (C) 1996 Elsevier Science Ltd [References: 21]
收起
摘要 :
Instead of 1,3-dipolar cycloaddition, the nucleophilic addition reaction proceeded smoothly between heterocyclic enamines 1 or 2 and nitrile imine 1,3-dipoles 3 under mild conditions to yield C-hydrazidoyl-substituted heterocyclic...
展开
Instead of 1,3-dipolar cycloaddition, the nucleophilic addition reaction proceeded smoothly between heterocyclic enamines 1 or 2 and nitrile imine 1,3-dipoles 3 under mild conditions to yield C-hydrazidoyl-substituted heterocyclic enamines 4-6 as the sole product. [References: 20]
收起
原文获取