Chiral Lewis acid catalysts in diels-Alder cycloadditions: mechanistic aspects and synthetic applications of recent systems

Fator de impacto de revistas científicas: qual o significado deste parâmetro?

“…A Tabela 1 contém exemplos que ilustram alguns dos erros mais freqüentes. Um outro exemplo, recente, envolvendo a revisão publicada por Dias 10 . A situação financeira das instituições de pesquisas, muito mais crítica do que a americana em outras partes do mundo, dá uma dimensão do que poderá ocorrer no Brasil nos próximos anos se os recursos para a aquisição de periódicos continuarem a diminuir, como, aliás, aconteceu com os recentes cortes feitos pela CAPES para as assinaturas das revistas, em 1999.…”

The Diels-Alder reaction: an update

“…With the basic and relevant empirical facts well established, and the Woodward-Hoffmann rules allowing predictability of the expected structures to be produced in the classical intermolecular reaction, it became of interest to study ways to alter or circumvent the observed chemo-, regio-and stereoselectivities, and induce enantioselectivity 28 . These aspects will be considered within the discussion of the intramolecular Diels-Alder (IMDA) reaction [29][30][31][32][33][34][35][36] .…”

Green approach using water mediated Diels-Alder reaction for the synthesis of some 2-(4-bromo-1-naphthyl)-3-(aryl) bicyclo[2.2.1]hept-5-ene methanones and evaluation of their antimicrobial and antioxidant activities

“…The water mediated environmentally benign hetero Diels-Alder [4+2] cycloaddition reaction was 700 times faster than in nonaqueous phase [3]. Numerous catalysts were employed to perform this Diels-Alder reaction, such as specific and chiral Lewis acids [3,15], chiral bases [16], chiral amines [5,6], non-natural α-amino acids [17], bimodal catalysts [18], hydrogen bonding interactions [1], chiral silver phosphates [4], Ti(IV) compounds [19], alkaline salts [20], lithium perchlorate [10], pyridyl-modified RNA [11], fly-ash [21][22][23][24][25], carbocations [13], Cu(II) compounds [2], organo-tungstates with ionicliquids [26], ribozymes [27], low melting carbohydrates [28], and metal-free non-covalent compounds [29]. Fard et al have studied the solvent effect and performed DFT analysis of acid catalyzed Diels-Alder cycloaddition reaction of 2,5-dimethyl furan and maleic anhydride [30].…”