Triphosgene and DMAP as Mild Reagents for Chemoselective Dehydration of Tertiary Alcohols
作者:Moshood O. Ganiu、Alexander H. Cleveland、Jarrod L. Paul、Rendy Kartika
DOI:10.1021/acs.orglett.9b01959
日期:2019.7.19
The utility of triphosgene and DMAP as mild reagents for chemoselective dehydration of tertiary alcohols is reported. Performed in dichloromethane at room temperature, this reaction is readily tolerated by a broad scope of substrates, yielding alkenes preferentially with the (E)-geometry. While formation of the Hofmann products is generally favored, a dramatic change in alkene selectivity toward the
“On water” sp3–sp2 cross-couplings between benzylic and alkenyl halides
作者:Valeria Krasovskaya、Arkady Krasovskiy、Anish Bhattacharjya、Bruce H. Lipshutz
DOI:10.1039/c1cc11087j
日期:——
Organic-solvent-free cross-couplings between benzylic and alkenylhalides have been developed. Various alkenylhalides can be efficiently benzylated by combining the precursor halides in the presence of Zn dust and a Pd catalyst at room temperature, in water as the only medium.
Enecarbamates as Selective Substrates in Oxidations: Chiral-Auxiliary-Controlled Mode Selectivity and Diastereoselectivity in the [2+2] Cycloaddition and Ene Reaction of Singlet Oxygen and in the Epoxidation by DMD and <i>m</i>CPBA
作者:Waldemar Adam、Sara G. Bosio、Nicholas J. Turro、Barbara T. Wolff
DOI:10.1021/jo035745c
日期:2004.3.1
The stereochemical course of the oxidation of chiral oxazolidinone-substituted enecarbamates has been studied for singletoxygen (1O2), dimethyldioxirane (DMD), and m-chloroperbenzoic acid (mCPBA) by examining of the special structural and stereoelectronic features of the enecarbamates. Valuable mechanistic insight into these selective oxidations is gained. Whereas the R1 substituent on the chiral
手性恶唑烷酮取代enecarbamates氧化的立体化学过程已经研究了单重态氧(1 Ò 2),二甲基二(DMD),和中号氯过苯甲酸(米通过的enecarbamates的特殊的结构和立体电子特征检查CPBA) 。获得了对这些选择性氧化的有价值的机理见解。而手性助剂上的R 1取代基负责双键的空间屏蔽,并决定π面非对映选择性的感觉,Z / E构型等结构特征和R 2的性质双键上的基团负责非对映选择性的程度。在1 O 2的情况下,通过乙烯基氮官能团进行的立体电子控制可控制模式选择性(烯反应与[2 + 2]环加成反应)。
Catalytic Intermolecular Tail-to-Tail Hydroalkenylation of Styrenes with α Olefins: Regioselective Migratory Insertion Controlled by a Nickel/N-Heterocyclic Carbene
作者:Chun-Yu Ho、Lisi He
DOI:10.1002/anie.201001849
日期:2010.11.22
first single‐operation, highly selective intermolecular tail‐to‐tail hetero‐hydroalkenylation from two readily available monosubstituted alkenes is described (see scheme; IPr=1,3‐Bis(2,6‐di‐isopropylphenyl)imidazol‐2‐ylidene). The reaction is catalyzed by the proposed [(IPr)NiH]OTf species. The method allows the use of more common and structurally diverse αolefins as substrates, which were previously
Highly Diastereoselective Dioxetane Formation in the Photooxygenation of Enecarbamates with an Oxazolidinone Chiral Auxiliary: Steric Control in the [2 + 2] Cycloaddition of Singlet Oxygen through Conformational Alignment
作者:Waldemar Adam、Sara G. Bosio、Nicholas J. Turro
DOI:10.1021/ja026815k
日期:2002.7.1
The photooxygenation of oxazolidinone-substituted enecarbamates leads to diastereomerically pure dioxetanes. The high diastereoselectivity is rationalized in terms of effective pi-facial control achieved by shielding one side of the double bond with the chiral auxiliary. The absolute configuration of the dioxetanes is assigned by derivatization to diols.
恶唑烷酮取代的烯氨基甲酸酯的光氧化产生非对映异构纯的二氧杂环丁烷。就通过用手性助剂屏蔽双键的一侧实现的有效 pi 面控制而言,高非对映选择性是合理的。二氧杂环丁烷的绝对构型通过衍生化分配给二醇。