Brønstedacidscatalyze the addition of enolizable β-diketones, β-ketoesters, and vinylogous amides to α,β-unsaturated aldehydes to lead to substituted chromenones, pyranones, and tetrahydroquinolinones in good yields under mild reaction conditions via a formal [3 + 3] cycloaddition.
Brønstedacidscatalyze the addition of enolizable β-keto esters to α,β-unsaturated aldehydes leading to substituted 2H-pyrans in good yields under mild conditions via a formal [3+3] cycloaddition.
The chemistry of coumarin derivatives, part 2. Reaction of 4-hydroxycoumarin with ?,?-unsaturated aldehydes
作者:Giovanni Appendino、Giancarlo Cravotto、Silvia Tagliapietra、Gian Mario Nano、Giovanni Palmisano
DOI:10.1002/hlca.19900730709
日期:1990.10.31
4-Hydroxycoumarin (= 4-hydroxy-2H-1-benzopyran-2-one) reacts with enals to give 1,2- or 1,4-addition products, depending on the nature and relative location of the substituents on the olefinic double bond (Scheme 2). The resulting adducts further react intra- or intermolecularly, affording dimeric coumarins or pyranocoumarins in the case of 1,2-addition and acetalic pyranocoumarins in the case of 1,4-addition. With
4-羟基香豆素(= 4-羟基-2 H -1-苯并吡喃-2-酮)与烯醛反应生成1,2-或1,4-加成产物,具体取决于烯基上取代基的性质和相对位置双键(方案2)。所得的加合物进一步在分子内或分子间反应,在1,2-加成的情况下提供二聚香豆素或吡喃香豆素,在1,4-加成的情况下提供乙缩醛吡喃香豆素。带有在C(β)处带有烷基的烯醛,仅形成2 H-吡喃并[3,2- c ]香豆素,该反应代表了轻松而直接地进入最近描述的此类具有生物活性的天然产物的类别。
APPENDINO, GIOVANNI;CRAVOTTO, GIANCARLO;TAGLIAPIETRA, SILVIA;NANO, GIAN M+, HELV. CHEM. ACTA., 73,(1990) N, C. 1865-1878
作者:APPENDINO, GIOVANNI、CRAVOTTO, GIANCARLO、TAGLIAPIETRA, SILVIA、NANO, GIAN M+
DOI:——
日期:——
Microwave-Assisted Solvent and Catalyst Free Synthesis of 2H-Pyrans
作者:Naushad Edayadulla、Yong Rok Lee
DOI:10.5012/bkcs.2013.34.10.2963
日期:2013.10.20
This paper describes a simple and efficient method involving domino Knovenegal/$6\pi}$ electrocyclization for the preparation of a variety of 2H-pyrans using microwave irradiation under solvent- and catalyst-free conditions. This method offers the advantages of a green approach, high yields, and short reaction times. Sixteen compounds (9a-p) were obtained in good to excellent yields using the procedure.