Diazo Transfer Reactions to 1,3-Dicarbonyl Compounds with Tosyl azide

International audienceA practical protocol for the large-scale preparation of 2-diazo-1,3-dicarbonyl compounds is described by diazo-transfer reactions with tosyl azide followed by efficient chromatographic purifications on silica gel and/or alumina

Preparation of mono-substituted malonic acid half oxyesters (SMAHOs).

The use of mono-substituted malonic acid half oxyesters (SMAHOs) has been hampered by the sporadic references describing their preparation. An evaluation of different approaches has been achieved, allowing to define the best strategies to introduce diversity on both the malonic position and the ester function. A classical alkylation step of a malonate by an alkyl halide followed by a monosaponification gave access to reagents bearing different substituents at the malonic position, including functionalized derivatives. On the other hand, the development of a monoesterification step of a substituted malonic acid derivative proved to be the best entry for diversity at the ester function, rather than the use of an intermediate Meldrum acid. Both these transformations are characterized by their simplicity and efficiency, allowing a straightforward access to SMAHOs from cheap starting materials

Periselectivity in the Aza-Diels–Alder Reaction of 1-Azadienes with α-Oxoketenes: A Combined Experimental and Theoretical Study

Inversions in the periselectivity of formal aza-Diels–Alder cycloadditions between α-oxoketenes generated by a thermally-induced Wolff rearrangement and 1-azadienes were observed experimentally as a function of the α-oxoketene and the 1-azadiene, as well as the reaction temperature and time. Some unexpected inversion in the diastereoselectivity was observed, too. These variations in selectivities were fully rationalized by computational modeling using density functional theory (DFT) methods

Microwave-Assisted Domino and Multicomponent Reactions with Cyclic Acylketenes: Expeditious Syntheses of Oxazinones and Oxazindiones

International audienceThe microwave-assisted Wolff rearrangement of cyclic 2-diazo-1,3-diketones in the presence of aldehydes and primary amines provides a straightforward access to functionalized bi- and pentacyclic oxazinones following an unprecedented three-component domino reaction. Alternatively, in the presence of acyl azides, an efficient Curtius/Wolff/hetero-Diels-Alder sequence allows the direct synthesis of oxazindiones

Quadrane Sesquiterpenes: Natural Sources, Biology, and Syntheses

International audienceQuadranes, discovered with the isolation of (-)-quadrone in 1978, are biologically active naturally occurring sesquiterpenes featuring a distinctive set of bi- to tetracyclic ring systems. The available data for this family of natural products, including isolation data, biosynthetic considerations, a comprehensive compilation of the reported biological activities, and an exhaustive survey of the synthetic work in this area so far, are critically analyzed

Syntheses and Applications of Functionalized Bicyclo[3.2.1]octanes: Thirteen Years of Progress

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Periselectivity Switch of Acylketenes in Cycloadditions with 1-Azadienes: Microwave-Assisted Diastereoselective Domino Three-Component Synthesis of alpha-Spiro-delta-lactams

International audienceThe microwave-assisted Wolff rearrangement of cyclic 2-diazo-1,3-diketones in the presence of primary amines and alpha,beta-unsaturated aldehydes provides a straightforward three-component stereoselective access to a variety of alpha-spiro-delta-lactams following an imination/Wolff rearrangement/[2 + 4] cycloaddition domino sequence. With aniline derivatives, a complementary aza-Wittig/Wolff rearrangement/[2 + 4] sequence was developed. These reactions feature an unprecedented reactivity of acylketenes as dienophiles in 6 pi electrocyclic processes

Catalyst-Free Formal Conjugate Addition/Aldol or Mannich Multicomponent Reactions of Mixed Aliphatic Organozinc Reagents, π-Electrophiles and Michael Acceptors

Catalyst-free multicomponent reactions of mixed alkylzinc reagents with Michael acceptors and aldehydes, ketones or activated imines are described. Primary, secondary and tertiary alkylzinc reagents, pre-generated in acetonitrile from the corresponding iodoalkanes, were used in the process, leading to the very efficient formation of a variety of β-hydroxycarbonyl compounds. The imines showed more contrasting results, due to the direct addition of the organozinc compound to the C=N bond. Mechanistic assays involving TEMPO account for a polar instead of a radical character of the reaction

Les composés 1,3-dicarbonylés en réactions domino et multicomposés : de l'approche synthétique des quadranes à la chimie des acycétènes

Les composés 1 3-dicarbonylés possèdent quatre centres réactionnels contigus avec une alternance de sites électrophiles et nucléophiles. Cette densité fonctionnelle en fait d'excellents substrats pour les réactions domino. Dans la première partie de ce manuscrit, un b-cétoester cyclique a ainsi été exploité pour la synthèse du système bicyclique BC des sesquiterpènes de la famille des quadranes en une seule opération. La réactivite particulière de cet intermédiaire a ensuite été étudiée vers leur synthèse totale. Dans la deuxième partie du manuscrit, le développement de la transposition de Wolffsous irradiation micro-ondes a permis un accès simple et efficace aux acylcétènes. Ces dérivés 1,3-dicarbonylés particuliers ont été exploités dans des réactions domino ioniques pour la synthèse de cycloalcanones [alpha]-carbonylées et d'hétérocycles, et dans des réactions péricycliques multicomposés pour la synthèse d'oxazinones, d' [alpha]-spiro-[delta]-lactames, et de pyrazolidinones.AIX-MARSEILLE3-BU Sc.St Jérô (130552102) / SudocSudocFranceF

Microwave-Assisted Wolff Rearrangement of Cyclic 2-Diazo-1,3-Diketones: An Eco-compatible Route to alpha-Carbonylated Cycloalkanones

International audienceThe microwave-assisted Wolff rearrangement of cyclic 2-diazo-1,3-diketones performed in the presence of a stoichiometric amount of alcohol, amine, or thiol is an efficient, user, and environmentally friendly synthetic protocol for the synthesis of alpha-carbonylated cycloalkanones. This approach proves superior to existing protocols in scope and eco-compatibility