Novel method for the synthesis of α- and β-halogenonaphthalenes by regioselective benzannulation of aryl(gem-dihalogenocyclopropyl)methanols: application to the total synthesis of the lignan lactones, justicidin E and taiwanin C¹

Antichagasic Activity of Lignans and Neolignans

“…Este crescente interesse se deve a grande diversidade de atividades biológicas que esta classe de compostos vem mostrando, como atividade contra leishmaniose, malária, doença de Chagas, anti-PAF, antitumoral, inseticida, atividade antimicrobiana, anti-inflamatória e analgésica. [8][9][10][11][12][13]…”

Hetero-Type Benzannulation Leading to Substituted Benzothio-Phenes

“…Taking this background into account, we envisaged a unique synthetic approach for the construction of benzothiophenes from counter thiophene cores, which is one type of benzannulation strategy (Scheme 2). Our group previously investigated primary nonregioselective [25] and secondary regiocontrolled [26,27] benzannulation methodologies; symmetrical (diaryl)(2,2-dichloro-1-methylcyclopropyl)methanols (AACM-1) and nonsymmetrical and stereodefined (aryl-1)(aryl-2)(2,2-dichloro-1-methylcyclopropyl)methanols (AACM-2) underwent the reactions to produce distinct 1-aryl-4-chloronaphthalene families bearing various substituents (Scheme 3). An ipso-variant of the regiocontrolled benzannulation for synthesizing uniquely substituted α-arylnaphthalenes and its application to the total synthesis of chaihunaphthone was also disclosed [27].…”

“…Following the reported procedure for the preparation of AACM-2 (Scheme 3) [10], the sequential introduction of Ar groups and a 1-thienyl group to acid chloride 2 provided stereodefined alcohols 13a and 13b in good yield with excellent stereoselectivity through ketones 12a [26] and 12b, respectively. The stereochemical course of the diastereoselective addition accounts for the reported mechanistic speculation based on the Cram rule [25][26][27]; the thienyl anion attacks the less hindered side of the more stable s-trans conformer of ketones 12 to afford stereodefined alcohols 13 with >95:5 de.…”

“…Following the reported procedure for the preparation of AACM-2 (Scheme 3) [10], the sequential introduction of Ar groups and a 1-thienyl group to acid chloride 2 provided stereodefined alcohols 13a and 13b in good yield with excellent stereoselectivity through ketones 12a [26] and 12b, respectively. The stereochemical course of the diastereoselective addition accounts for the reported mechanistic speculation based on the Cram rule [25][26][27]; the thienyl anion attacks the less hindered side of the more stable s-trans conformer of ketones 12 to afford stereodefined alcohols 13 with >95:5 de. With these successful results in hand, we investigated the functionalization of th obtained benzothiophenes 5, 11, and 14a to demonstrate the utility for synthesizing seve 4-aryl-substituted benzothiophene derivatives 15-21.…”

Synthetic nat- or ent-steroids in as few as five chemical steps from epichlorohydrin

“…Here, reaction of TiCl 4 with the D-ring hydroxy group (or with adventitious water) is thought to produce protic acid in situ and convert 10 to the reactive homoallylic cation intermediate II , presumably through a process that includes protodesilylation, protonation of the resulting styrenyl alkene, and regioselective cyclopropane fragmentation 36–39 . Ring closure would then be possible by engaging the phenyl ring in an intramolecular Friedel–Crafts alkylation to deliver an intermediate that is transformed to 12 through loss of HBr 40,41 .…”