A general and regioselective synthesis of substituted pyrroles 2 by cycloisomerization of readily available (Z)-(2-en-4-ynyl)amines 1 is reported. Spontaneous cycloisomerization leading to 2 occurred in the course of preparation of enynamines bearing a terminal triple bond or a triple bond substituted with a phenyl or a CH2OTHP group. When the triple bond was substituted with an alkyl or alkenyl group
Termination of cycliccarbopalladation of alkynes via carbonylative lactamization can be achieved more satisfactorily with alkenyl or aryl halides containing an ω-sulfonamido group than with those containing an ω-amino group. The method appears to be generally satisfactory for the preparation of fused cyclic systems consisting of six-membered rings, while the other cases require further development
Trapping of acylpalladium derivatives can be achieved using internal carboxamides and sulfonamides, in addition to simple amines and applied to termination of carbopalladation to produce lactams.
Synthesis of furans by base-catalyzed cyclization-isomerization of .beta.- and .gamma.-alkynyl allylic alcohols
作者:James A. Marshall、William J. DuBay
DOI:10.1021/jo00064a038
日期:1993.6
Beta- and gamma-alkylyl allylic alcohols 3, 13, 26, available through Pd-mediated coupling of appropriate vinylic halides and terminal alkynes, cyclize and subsequently isomerize to furans 4, 17, and 32 upon treatment with KO-t-Bu in t-BuOH-THF at 25-60-degrees-C. The methodology has been used to prepare 2,3-, 2,4-, and 2,3,5-substituted furans. Reactions in t-BuOD as cosolvent lead to deuterium incorporation consistent with concurrent pathways in which direct 5-exo-dig or 5-endo-dig cyclization of the alkynyl allylic alcohol competes with prior isomerization to an allene intermediate which subsequently cyclizes by 5-exo- or 5-endo-dig pathways.
Ruthenium-Catalyzed Cyclization of Alkyne−Epoxide Functionalities through Alternation of the Substituent and Structural Skeleton of Epoxides
作者:Lin Ming-Yuan、Reniguntala J. Madhushaw、Rai-Shung Liu
DOI:10.1021/jo048983w
日期:2004.10.1
Treatment of 1-(o-ethynylphenyl)-2-alkyl-2-aryl epoxides with TpRuPPh(3)(CH3CN)(2)PF6 catalyst (10 mol %) in hot toluene (100 degreesC, 12 h) led to an atypical cyclization and gave 1-aryl-2-alkyl-1H-indene derivatives and carbon monoxide efficiently. The cyclization of 1-cis-enynyl-2-alkyl epoxides with this catalyst in hot toluene (10 mol %, 100 degreesC, 12 h) gave 2,5-disubstituted phenols in 45-72% yields. Under the same conditions, 1-cis-enynyl-2,2-dialkyl epoxides and 1-cis-enynyl-2-alkyl-2-aryl epoxides gave the corresponding 6,6-disubstituted cyclohexa-2,4-dien-1-ones in good yields (85-91%). Mechanisms for these new cyclization reactions are proposed on the basis of trapping experiments and isotope labeling experiments. The formation of 1H-indene products likely involves ruthenium-acyl intermediates whereas cyclohexa-2,4-dien-1-ones are thought to derive from ruthenium-ketene intermediates.