炔丙醚与有机铜试剂反应,通过对三键进行顺式加成,然后β-消除生成的烯基铜物质来提供丙二烯。使用手性炔丙醚和化学计量有机铜试剂,表明 β-消除步骤是纯反的,导致形成具有 96% 光学产率的手性丙二烯。使用格氏试剂 RMgX 和催化量的 Cu I 盐进行相同的反应,通过反或顺整个过程提供丙二烯。关键的步骤是β-消除中间体烯基有机金属物种,它是反型与 RMgI 和顺型与 RMgCl。丙炔乙酸酯,在该反应中也提供丙二烯,但通过 Cu III 中间体,对这种“卤素效应”不敏感
Rhodium‐Catalyzed Parallel Kinetic Resolution of Racemic Internal Allenes Towards Enantiopure Allylic 1,3‐Diketones
作者:Lukas J. Hilpert、Bernhard Breit
DOI:10.1002/anie.201903365
日期:2019.7.15
parallel kinetic resolution of racemic 1,3‐disubstituted allenes by means of a rhodium‐catalyzed addition to 1,3‐diketones furnishing enantiopure allylic 1,3‐diketones is described. Mechanistic experiments demonstrate that the different allene enantiomers react in parallel to either the diastereomeric E‐ or Z‐allylic 1,3‐diketones with the same absoluteconfiguration of the newly formed stereogenic
Palladium‐ and Rhodium‐Catalyzed Dynamic Kinetic Resolution of Racemic Internal Allenes Towards Chiral Pyrazoles
作者:Lukas J. Hilpert、Simon V. Sieger、Alexander M. Haydl、Bernhard Breit
DOI:10.1002/anie.201812984
日期:2019.3.11
resolution (DKR) of racemic allenes leading to N‐allylated pyrazoles is described. Such compounds are of enormous interest in medicinal chemistry as certified drugs and potential drug candidates. The new methods feature high chemo‐, regio‐ and enantioselectivities aside from displaying a broad substrate scope and functional group compatibility. A mechanistic rational accounting for allene racemization and trans‐alkene
The carbonyldicobalt-mediated alkyne/allene/CO cocyclization gives 4-alkylidenecyclopentenones as the major [2+2+1] cycloadducts. The regio- and stereoselectivities depend mainly on the substitution pattern of both the alkyne and the allenic moieties, which can be rationalized using the Magnus mechanism. However, contrary to this model, and in agreement with more recent mechanistic studies, our results
allenylation, allylation, and annulation reactions. The outcome is governed by both the reactivity of the allene and the formation and stability of the organometallic intermediate. An efficient Rh(III)-catalyzed, weakly coordinating group-directed dienylation of electronically unbiased allenes is developed using an N-acyl amino acid as a ligand. Further elaboration of the dienylated products to construct
Synthesis of Linear Allylsilanes via Molybdenum-Catalyzed Regioselective Hydrosilylation of Allenes
作者:Sobi Asako、Sae Ishikawa、Kazuhiko Takai
DOI:10.1021/acscatal.6b00627
日期:2016.5.6
secondary and tertiary silanes proceeded smoothly and selectively to afford linear allylsilanes. The origin of the unprecedented linear selectivity was investigated by density functional theory studies to reveal that the reaction consists of the following steps: (1) concerted hydromolybdation/Si–H oxidative addition from a Mo(CO)4/allene/silane adduct to form (π-allyl)molybdenum, (2) allyl rotation from the