RESUMO
Allenes are useful functional groups in synthesis as a result of their inherent chemical properties and established reactivity patterns. One property of chemical bonding renders 1,3-substituted allenes chiral, making them attractive targets for asymmetric synthesis. While there are many enantioselective methods to synthesize chiral allenes from chiral starting materials, fewer methods exist to directly synthesize enantioenriched chiral allenes from achiral precursors. We report here an asymmetric boronate addition to sulfonyl hydrazones catalyzed by chiral biphenols to access enantioenriched allenes in a traceless Petasis reaction. The resulting Mannich product from nucleophilic addition eliminates sulfinic acid, yielding a propargylic diazene that performs an alkyne walk to afford the allene. Two enantioselective approaches have been developed; alkynyl boronates add to glycolaldehyde imine to afford allylic hydroxyl allenes, and allyl boronates add to alkynyl imines to form 1,3-alkenyl allenes. In both cases, the products are obtained in high yields and enantioselectivities.
Assuntos
Alcadienos/síntese química , Ácidos Borônicos/química , Hidrazonas/química , Fenóis/química , Alcadienos/química , Catálise , Estrutura Molecular , EstereoisomerismoRESUMO
Development of the self-assembled monolayer/MALDI mass spectrometry (SAMDI) platform to enable a high-throughput optimization of a traceless Petasis reaction is described. More than 1800 unique reactions were conducted simultaneously on an array of self-assembled monolayers of alkanethiolates on gold to arrive at optimized conditions, which were then successfully transferred to the solution phase. The utility of this reaction was validated by the efficient synthesis of a variety of di- and trisubstituted allenes.
Assuntos
Alcadienos/síntese química , Alcanos/química , Ouro/química , Ensaios de Triagem em Larga Escala , Compostos de Sulfidrila/química , Alcadienos/química , Técnicas de Química Combinatória , Estrutura Molecular , Espectrometria de Massas por Ionização e Dessorção a Laser Assistida por MatrizRESUMO
The development of a stereoselective one-pot oxidative [3,3]â sigmatropic rearrangement/Friedel-Crafts arylation that provides enantioenriched benzhydryl compounds is reported. The utility of this new transformation is demonstrated by the concise synthesis of several tetralone- and naphthyl-type lignan natural products, many of which display anti-malarial activity.
