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A novel, concise and efficient synthesis of substituted isocoumarins is disclosed. o-Allylbenzaldehydes prepared from isovanillin were mediated by PdCl2–CuCl2in water to undergo a domino reaction sequence, including 6-exo-trigcyclization, the addition of water, the elimination of PdHCl, the isomerization of carbon–carbon double bond, the oxidation of hemiacetals with the elimination of PdHCl, and regeneration of PdCl2in situto yield a series of new substituted isocoumarins in high yields, in one pot. [ABSTRACT FROM AUTHOR]

Abstract: A novel synthesis of substituted 3,4-dihydroisoquinolin-1(2H)-ones is described. o-Oxiranylmethylbenzonitriles, prepared from isovanillin via five synthetic steps, were treated with NaCN/tetra-n-butylammonium bromide (TBAB) to yield 3,4-dihydroisoquinolin-1(2H)-ones in good yields. This one pot reaction demonstrates the novel and chemoselective nature of ring-opening of epoxide by cyanide to generate an iminoisochroman ring via cyclization, again ring-opening by cyanide to generate a Michael acceptor and a donor, and ring re-cyclization through an intramolecular conjugate addition. The detailed mechanism is also rationally proposed. [Copyright &y& Elsevier]

Abstract: A mild, efficient, and regioselective carbanion–yne intramolecular cyclization mediated by t-BuOK for the synthesis of 2-substituted 3-benzylbenzofurans is developed. It was started from o-iodophenol (1), based on O-alkylation, and the Sonogashira reaction in sequence to produce 2-(2-phenylethynylphenoxy)-1-arylalkanones (5). An intramolecular carbanion–yne 5-exo-dig cyclization reaction of 5, which was mediated by t-BuOK, yielded title benzofurans in good yields. [Copyright &y& Elsevier]

Abstract: Mild and environmentally benign methods for the syntheses of flavanones are described. The reaction of o-hydroxyacetophenones (1) and benzaldehydes (2) in water in the presence of DABCO at room temperature gave 3-hydroxy-1-(2-hydroxylphenyl)-3-arylpropan-1-ones (3a–i) as intermediates. Followed by an intramolecular dehydration of the 3a–i with the modified Mitsunobu’s reaction, the target flavanones (4a–i) were obtained. Moreover, the reaction of 1 and 2 at the same conditions but at reflux gave flavanones in one pot with good yields. [Copyright &y& Elsevier]

Abstract: New syntheses of haginin E, equol, daidzein, and formononetin are described in this Letter. Through a sequence of a Wittig reaction, O-alkylation, and another Wittig reaction, 4-benzyloxysalicylaldehyde, which was prepared from resorcinol in two steps, was converted into the desired diene in one pot. Subsequently, the prepared diene was subjected to ring-closing metathesis using Grubbs’ catalyst (II) to construct the desired isoflavene intermediate. Using the prepared isoflavene, certain isoflavonoids such as haginin E, equol, daidzein, formononetin, and other related compounds were derived smoothly and in good overall yields. [Copyright &y& Elsevier]

Abstract: Utilization of a novel carbanion-olefin intramolecular 6-endo-trig cyclization reaction to provide 2-aroyl-3,4-dihydro-2H-benzopyrans is described. Through a sequence of a Wittig reaction, O-alkylation, and carbanion-olefin intramolecular cyclization, salicylaldehydes were converted into a series of new 2-aroyl-3,4-dihydro-2H-benzopyrans in two steps or in one-pot reaction. [Copyright &y& Elsevier]

Abstract: The synthesis of substituted 2-aroyl-3-methylchromen-4-one from isovanillin is described. O-Allylphenol (2) prepared from isovanillin (1) was allowed to react with various α-bromoacetophenone (3) to produce 2-(2-allyl-3,4-dimethoxy)phenoxy-1-aroylethanones (4). The resultant 4 were treated with 2equiv of potassium tert-butoxide to afford the substituted 2-aroyl-3-methylchromans (5) through an isomerization of an allylic double bond and a carbanion–olefin intramolecular 6-endo-trig cyclization reaction. Subsequently, resultant 5 were oxidized with DDQ to yield the title compound 6, in good over-all yields. [Copyright &y& Elsevier]