Palladium‐Catalyzed Asymmetric Iodination of Unactivated CH Bonds under Mild Conditions

Abstract

The catalytic activation of C(sp 3 )ÀH and C(sp 2 )ÀH bonds in readily available, inexpensive starting materials would provide a valuable array of new transformations for organic chemistry research and the fine chemical industry.[1] Activation of C(sp 2 )ÀH bonds in benzene and ortho-substituted arenes has been successfully exploited in the development of catalytic CÀC bond-forming reactions by coupling to olefins. [2,3] The selective activation of C(sp 3 )ÀH bonds under mild conditions could be an attractive strategy for the development of catalytic reactions with wide applicability. Despite extensive efforts that have focused mainly on carbene and nitrene insertions, metathesis, Shilov chemistry, and biomimetic approaches, the catalytic and asymmetric functionalization of C(sp 3 )ÀH bonds remains a significant challenge.[4]We report herein an auxiliary approach for the chemoselective and asymmetric room-temperature iodination of

Easily Accessible Auxiliary for Palladium‐Catalyzed Intramolecular Amination of C(sp2)H and C(sp3)H Bonds at δ‐ and ε‐Positions

“…[15] To get a better understanding on the reaction mechanism, we tried to isolate and identify the [a]…”

Diastereoselective Substrate-Controlled Transition-Metal-Catalyzed C–H Activation: An Old Solution to a Modern Synthetic Challenge

“…In this context, the seminal work of Yu on asymmetric C-H activation represented a real breakthrough. 7 Yu and co-workers surmised that the oxazoline moiety might be used as an efficient σ-chelating DG that would facilitate the assembly of a pretransition state for cyclometallation through a square-planar complex. This assumption was initially confirmed by conducting a palladium-mediated stoichiometric iodination of an aliphatic pivalic acid substrate to give a monoiodinated product in a high (80%) yield.…”

“…In 2005, however, Yu and co-workers demonstrated that chiral compounds can be generated by direct functionalization of C-H bonds, provided that a chiral directing group is embedded within a substrate and coordinates the metal catalyst to permit the formation of a stereogenic metallacyclic intermediate in the key C-H bond-cleavage step. 7 Despite the importance of this seminal work, stereoselective C-H activation remained a niche topic until about 2010, when interest in asymmetric direct functionalization was revived. At this time, the development of enantioselective transformations became clearly favored.…”

Recent Advances on Transition-Metal-Catalyzed Halogenation of Unactivated C-H Bonds

“…近年来, 过渡金属催化的碳氢键官能团化反应 [6] 受 到广泛关注, 并已成为在有机化合物中引入特定官能团 的更为原子经济性和绿色高效的策略 [7] . 其中, 过渡金 [9] (图 2, 式 1)和 Yu 课题组 [10] (图 2, 式 2)…”

“…以 N-卤代酰亚胺为卤源, Gevorgyan [16] 、Sun [17] [10,24] 利用具有位阻的恶唑啉为导向基团, 以碘单质为碘源完 成了 sp 3 碳氢键的不对称碘代反应(图 2, 式 2). 通过改 变碘代试剂的当量, 也能够实现两个甲基的双碘代 [25] (图 7, 式 1).…”