29478-27-1Relevant articles and documents
EFFECTS ISOTOPIQUES DU DEUTERIUM EN RMN 13C. MESURE DU MARQUAGE ISOTOPIQUE DES ALCOOLS ALLYLIQUES.
Smadja, William
, p. 3945 - 3948 (1988)
Primary and secondary deuterium isotope effects on 13C NMR chemical shifts for trigonal carbons are reported for twelve allylic alcohols.The secondary DIECCS is used for an accurate measurement of the deuterium labeling of variously substituted allylic alcohols.
Synthetic and Computational Study of Tin-Free Reductive Tandem Cyclizations of Neutral Aminyl Radicals
Sirinimal, Hansamali S.,Hebert, Sebastien P.,Samala, Ganesh,Chen, Heng,Rosenhauer, Gregory J.,Bernhard Schlegel,Stockdill, Jennifer L.
supporting information, p. 6340 - 6344 (2018/10/09)
5-exo, 5-exo Cyclizations of conformationally unbiased propargylic aminyl radicals proceed with excellent yield, chemoselectivity, and diastereoselectivity under tin-free reductive cyclization conditions, regardless of the electronic environments and intermediate radical stabilization resulting from various olefin substituents. These conditions avoid the need for slow addition of initiator and reductant. By contrast, analogous 6-exo, 5-exo cyclizations require substituents capable of intermediate radical stabilization to avoid premature reduction products. These experimental results are corroborated by computations that further establish the reactivity of these aminyl radicals upon exposure to tin-free cyclization conditions.
Gold(I)-catalyzed highly regio- and stereoselective decarboxylative amination of allylic N-tosylcarbamates via base-induced aza-Claisen rearrangement in water
Xing, Dong,Yang, Dan
supporting information; experimental part, p. 1068 - 1071 (2010/06/13)
(Figure Presented)A gold(l)-catalyzed decarboxylative animation of allylic N-tosylcarbamates via base-induced aza-Claisen rearrangement has been developed. A variety of substituted W-tosyl allylic amines were obtained In good yield, excellent regloselectlvity, and high to excellent stereoselectivity. This transformation could be performed either in H2O or In one pot directly from allylic alcohols and therefore represents an efficient and environmentally benign protocol for the synthesis of N-tosyl allylic amines.
Preparation of stereodefined homoallylic amines from the reductive cross-coupling of allylic alcohols with imines
Chen, Ming Z.,McLaughlin, Martin,Takahashi, Masayuki,Tarselli, Michael A.,Yang, Dexi,Umemura, Shuhei,Micalizio, Glenn C.
supporting information; experimental part, p. 8048 - 8059 (2011/02/26)
Regio-, diastereo-, and enantioselective coupling reactions between imines and allylic alcohols have been developed. These coupling reactions deliver complex homoallylic amine products through a convergent C-C bond forming process that does not proceed through intermediate allylic organometallic reagents. In general, convergent coupling, by exposure of an allylic alkoxide to a preformed Ti-imine complex, occurs with allylic transposition in a predictable and stereocontrolled manner. While simple diastereoselection in these reactions is high, delivering anti-products with ≥20:1 selectivity, the organometallic transformation described is compatible with a diverse range of functionality and substrates (including aliphatic and aromatic imines, allylic silanes, trisubstituted alkenes, vinyl- and aryl halides, trifluoromethyl groups, thioethers, and aromatic heterocycles). Alkene geometry of the products is a complex function of the allylic alcohol structure and is consistent with a mechanistic proposal based on syn-carbometalation followed by syn-elimination by way of a boat-like transition state geometry. Single asymmetric coupling reactions provide a means to translate the stereochemical information of the allylic alcohol to the homoallylic amine or to control diastereoselection in the coupling reactions of achiral allylic alcohols with chiral imines. Double asymmetric coupling reactions are also described that afford a unique means to control stereoselection in these complex convergent coupling processes. Finally, empirical models are proposed that are consistent with the observed stereochemical course of these coupling reactions en route to chiral homoallylic amines possessing di- or trisubstituted alkenes and anti- or syn- relative stereochemistry at the allylic and homoallylic positions.
Reduction of α,β-unsaturated ketones with diphenylsilanes bearing several substituents on their phenyl moiety catalyzed by rhodium-phosphine complexes
Imao, Daisuke,Hayama, Miyuki,Ishikawa, Kohta,Ohta, Tetsuo,Ito, Yoshihiko
, p. 366 - 367 (2007/10/03)
1,4-Addition product was afforded exclusively by rhodiumphosphine complex-catalyzed hydrosilylation by using 2-cyclohexen-1-one and a dihydrosilane bearing an ether substituent in spite of the fact that dihydrosilanes were believed to give 1,2-addition product selectively. Copyright
Iterative deoxypropionate synthesis based on a copper-mediated directed allylic substitution: Formal total synthesis of borrelidin (C3-C11 fragment)
Herber, Christian,Breit, Bernhard
, p. 6684 - 6691 (2008/09/17)
A new iterative strategy for the flexible preparation of any oligodeoxypropionate stereoisomer is presented which relies on an o-DPPB-directed copper mediated allylic substitution employing enantiomerically pure Grignard reagents; the reaction is working with perfect control over all aspects of the reaction selectivity. This key C-C bond-forming step features reversed polarity compared with established enolate alkylation methodology. It thus avoids existing problems of enolate alkylation strategies such as enolate reactivity as well as costs and problems associated with the chiral auxiliary. Practicability of this new method is demonstrated through application in natural product syntheses. Thus, an efficient synthesis of the northern part of the angiogenesis inhibitor borrelidin (28), the deoxypropionate building block 27, could be devised, representing a formal total synthesis.
Iterative deoxypropionate synthesis based on a copper-mediated directed allylic substitution
Breit, Bernhard,Herber, Christian
, p. 3790 - 3792 (2007/10/03)
Can't have too much of a good thing: A flexible, iterative strategy based on a highly selective copper-mediated allylic substitution makes the preparation of any desired oligo(deoxypropionate) stereoisomer possible (see scheme; RDG = reagent-directing group). This approach differs from the established enolate-alkylation methodology through the reversed polarity of the reaction partners and avoids several problems associated with the latter method.
A convenient synthesis of piperidine-based β-amino alcohols from L-Phe and highly enantioselective addition of diethyl zinc to aldehydes
Da, Chao-Shan,Han, Zhi-jian,Ni, Ming,Yang, Fan,Liu, Da-Xue,Zhou, Yi-Feng,Wang, Rui
, p. 659 - 665 (2007/10/03)
β-Amino alcohols 4a-e were easily prepared from L-phenylalanine in three simple straightforward steps. The key intermediate compound (S)-3 was achieved in high yield (up to 92%) with glutaraldehyde and NaBH4/H2SO4 in THF at room temperature. These five ligands were applied to catalyze enantioselective addition of diethyl zinc to aldehydes, high asymmetric induction was observed with 4c and 4e, and the ee value was up to 98%. The effect of the substitutes on the nitrogen atom was also observed via comparing piperidine-based amino alcohols with pyrrolidine-based similar ligands.
In situ 1H-PHIP-NMR studies of the stereoselective hydrogenation of alkynes to (E)-alkenes catalyzed by a homogeneous [Cp*Ru]+ catalyst
Schleyer,Niessen,Bargon
, p. 423 - 426 (2007/10/03)
The hydrogenation of internal alkynes using a [Cp*Ru(alkene)]+ complex leads to the formation of (E)-alkenes. This ruthenium complex represents one of the few homogeneous catalysts that trans-hydrogenate internal alkynes directly and stereoselectively. We have studied its stereoselectivity by in situ PHIP-NMR spectroscopy (PHIP = para-hydrogen induced polarization). With this method the initially formed products can be identified and characterized even at very low concentrations and low conversions. Furthermore, their subsequent fate can be evaluated with high sensitivity and with time resolution. Different alkyne substrates were used to demonstrate the universal applicability of this catalyst. The catalyst is not active in combination with terminal alkynes, however, possibly due to the formation of a rather stable vinylidene complex. A mechanism proceeding via a binuclear complex is proposed to explain the formation of the (E)-alkenes.
Engineering catalysts for enantioselective addition of diethylzinc to aldehydes with racemic amino alcohols: Nonlinear effects in asymmetric deactivation of racemic catalysts
Long, Jiang,Ding, Kuiling
, p. 544 - 547 (2007/10/03)
Correct additions make a difference: Asymmetric deactivation and asymmetric amplification concepts coupled with a high-throughput screening technique provided a successful strategy for designing a highly enantioselective catalytic system by simple combination of a racemic amino alcohol (rac-DB) and a nonracemic additive (AA). The example in the scheme shows the conversion of 1 into 2 with up to 92.7% ee.
