Gas phase thermalisomerizations of twelve acetylenic systems, all of which can in principle undergo two successive pericyclic steps, are described. The substrates, the syntheses and spectroscopic properties of which are presented, are formal derivatives of but-2-yne, with different functional groups in the 1- and the 4-positions. The Cope, Claisen, Claisen ester, retro-ene, 1,5-hydrogen shift, and
New Dienophiles: 1-Acetylvinyl Arenecarboxylates. Reactivity toward cyclopentadiene and exocyclic dienes
作者:Joaquin Tamariz、Pierre Vogel
DOI:10.1002/hlca.19810640121
日期:1981.2.4
these dienophiles toward cyclopentadiene is evaluated and compared with that of methyl vinylketone, 3-trimethylsilyloxy-, 3-ethoxy- and 3-acetoxy-3-buten-2-ones. The stereoselectivity of the cycloadditions of these dienophiles with 2,3,5,6-tetramethylidene-7-oxanorbornane (1) and 5,8-dimethoxy-1,4-epoxy-2,3-dimethylidene-1,2,3,4-tetrahydroanthracene (2) is studied. In principle, the dienophiles 3 allow
描述了1-乙酰乙烯基芳烃羧酸盐H 2 C = C(COCH 3)OCOR的制备,其中R =苯基,对硝基苯基,2,4-二硝基苯基,α-和β-萘基(3)。评估了这些亲二烯体对环戊二烯的Diels-Alder反应性,并将其与甲基乙烯基酮,3-三甲基甲硅烷基氧基-,3-乙氧基-和3-乙酰氧基-3-丁烯-2-酮的反应进行了比较。这些亲二烯体与2,3,5,6-四亚甲基-7-氧杂硼烷(1)和5,8-二甲氧基-1,4-环氧-2,3-二甲基-1,2,3的环加成反应的立体选择性,研究了4-四氢蒽(2)。原则上,双亲物3允许Diels-Alder加成到环外二烯(例如1和2)的Diels-Alder中,将道诺维素类似物A环的位置C(9)直接官能化。
Highly selective 1,3-dipolar cycloadditions of captodative olefins 1-acetylvinyl carboxylates to diverse dipoles
Regioselective 1,3-dipolarcycloadditions of captodative 1-acetylvinyl p-nitrobenzoyloxy (1a) with propionitrile oxide, diphenylnitrile imine and diazoalkanes provided the corresponding 5-acetyl- isoxazoles and pyrazoles. Evidence to support the formation of the initial cycloadducts was obtained. The addition of nitrones also proved to be highly regio- and stereoselective.
Regio- and Stereoselectivity of Captodative Olefins in 1,3-Dipolar Cycloadditions. A DFT/HSAB Theory Rationale for the Observed Regiochemistry of Nitrones
作者:Rafael Herrera、Arumugam Nagarajan、Miguel A. Morales、Francisco Méndez、Hugo A. Jiménez-Vázquez、L. Gerardo Zepeda、Joaquín Tamariz
DOI:10.1021/jo001393n
日期:2001.2.1
Captodative olefins 1-acetylvinyl carboxylates proved to be highly regioselective dipolarophiles in 1,3-dipolar cycloadditon to propionitrile oxide, arylphenylnitrile imines, diazoalkanes, and nitrones to yield the corresponding 5-substituted heterocycles. The addition of the latter was also stereoselective, being slightly susceptible to steric demand of the carboxylate substituent in the olefin. All atempts
2-dimethylaminomethyl-3-trimethylsilylmethyl-1,3-butadiene as 2,2′-biallyl diradical synthon. A new and facile entry to 1,2-dimethylenecyclohexanes, and [6.6] and (6.7] ring systems
作者:Akira Hosomi、Ken Otaka、Hideki Sakurai
DOI:10.1016/s0040-4039(00)84669-9
日期:1986.1
compound, prepared readily by the cross-coupling reaction of β-bromoallyltrimethylsilane and the Grignard reagent from β-bromoallyldimethylamine, is an effective reagent as 2,2′-biallyl diradical synthon to give [6.6] and [6.7] ringsystems by tandem cycloaddition reactions. 1,2-Dimethylenecyclohexanes can also be isolated in good yield.