Oligo(cyclohexylidenes): Parent Compounds and End-Functionalized Derivatives
摘要:
Parent oligo(cyclohexylidenes) 1(n) (n = 1-4) were synthesized using a modified Barton-Kellogg olefin synthesis. Surprisingly, the crude compounds 1(2) and 1(4) contained small amounts of the 1(n-1) and 1(n+1) homologues. As evidenced by a close examination of mass spectral data of selectively deuterated tercyclohexylidenes 1(2)d(4)d(4) and 1(2)-d(8), their formation can be attributed to scrambling of the intermediate azines. With increasing n, a marked decrease in solubility as well as an increase in thermal stability was found. Powder diffraction measurements indicate that the parent compounds 1(n), irrespective of n, pack in a similar fashion in the solid state. The theoretically (MMX, AM1, and ab initio) predicted rodlike structure of the oligo(cyclohexylidenes) was confirmed by single-crystal X-ray structures of 1(1) and three derivatives (12(1), 13(1), and 30(2)). In line with the powder diffraction data in the series 1(n), a similar packing motif was found for the derivatives. To circumvent side product formation due to azine scrambling, a different synthetic approach was used for the preparation of end-functionalized oligo(cyclohexylidenes), i.e. decarboxylation and dehydration of beta-hydroxy acids.
作者:Paul J. Kropp、Norbert J. Pienta、Joy A. Sawyer、Richard P. Polniaszek
DOI:10.1016/s0040-4020(01)92370-1
日期:——
The previously observed cyclopropaoation of alkenes by irradiation of diiodomethane (I) in their presence has been studied in more detail and found to be a synthetically useful procedure which is significantly less subject to steric effects than the traditional Simmons-Smith method. The results from photocyclopropanation of a variety of alkenes are summarized in Tables 1 and 3–4. In a number of cases
Intermolecular [2 + 2] Photocycloaddition of α,β-Unsaturated Sulfones: Catalyst-Free Reaction and Catalytic Variants
作者:Noah Jeremias、Lisa-Marie Mohr、Thorsten Bach
DOI:10.1021/acs.orglett.1c01794
日期:2021.8.6
2-Aryl-1-sulfonyl-substituted cyclobutanes were prepared in an intermolecular [2 + 2] photocycloaddition from various α,β-unsaturated sulfones and olefins upon irradiation at λ = 300 nm (26 examples, 60–99% yield). Lewisacids catalyzed the [2 + 2] photocycloaddition of 2-benzimidazolyl styryl sulfones. At short wavelengths, the latter substrates underwent C–S bond cleavage but AlBr3 (5 mol %) allowed
REDUCTION OF AROMATIC AND ALIPHATIC NITRO COMPOUNDS BY SODIUM HYDROGEN TELLURIDE
作者:Atsuhiro Osuka、Hirohito Shimizu、Hitomi Suzuki
DOI:10.1246/cl.1983.1373
日期:1983.9.5
Various nitro compounds were effectively reduced by sodium hydrogen telluride in good yields. Thus, reductive conversion of unhindered nitrobenzenes to azoxybenzenes, sterically hindered nitrobenzenes to anilines, nitroalkanes to dimer of nitrosoalkanes, and vicinal-dinitroalkane to olefin was achieved.
Regioselective and Stereospecific Copper-Catalyzed Deoxygenation of Epoxides to Alkenes
作者:Jingxun Yu、Yu Zhou、Zhenyang Lin、Rongbiao Tong
DOI:10.1021/acs.orglett.6b02405
日期:2016.9.16
diazo malonate for chemo-/regioselective and stereospecificdeoxygenation of various epoxides with tolerance of common functional groups (alkene, ketone, ester, p-methoxybenzyl, benzyl, tert-butyldimethylsilyl, and triisopropylsilyl). In particular, the unprecedented regioselectivity allowed for the first time monodeoxygenation of diepoxides to alkenyl epoxides. Density functional theory mechanistic studies
两种铜盐(Cu(CF 3 CO 2)2和IMesCuCl)被鉴定为是地球上丰富的,廉价的但有效的金属催化剂,与重氮丙二酸酯一起用于各种环氧化物的化学/区域选择性和立体定向脱氧反应,并具有常见的官能团耐受性(烯烃,酮,酯,对甲氧基苄基,苄基,叔丁基二甲基甲硅烷基和三异丙基甲硅烷基)。特别是,空前的区域选择性使二环氧化物首次单脱氧为烯基环氧化物。密度泛函理论的机理研究表明,脱氧是通过折叠游离的叶立德而发生的,不利于通过可能的氧杂环丁烷的环还原而产生的直观途径。
Hydroalumination of alkenes by the LiAlH4 � 3AlBr3 system
作者:E. V. Gorobets、O. V. Shitikova、S. I. Lomakina、G. A. Tolstikov、A. V. Kuchin
DOI:10.1007/bf00699198
日期:1993.9
3AlBr3 system in low-polar solvents was studied. Alkenes with mono-, di-, tri-, and tetraalkyl substituted, mono- and diaryl substituted doublebonds and anthracene react at room temperature to give the corresponding dibromoaluminoalkanes in high yields. Benzylidenefluorene, tetraphenylethylene, naphthalene, and phenanthrene do not undergo hydroalumination under these conditions. Camphene, bicyclo[3.2