Blog

Flexible Reaction Pocket on Bulky Diphosphine–Ir Complex Controls Regioselectivity in para-Selective C–H Borylation of Arenes

Brandon E. Haines, Yutaro Saito, Yasutomo Segawa, Kenichiro Itami, and Djamaladdin G Musaev

ACS Catal. 2016, 6, 7536–7546. DOI: 10.1021/acscatal.6b02317

We used DFT calculations to elucidate the mechanism and source of regioselectivity for Ir-catalyzed para-selective C–H borylation with the bulky Xyl-MeO-BIPHEP diphosphine ligand (L1). We found that the bulky diphosphine–Ir complex forms a flexible reaction pocket that roughly mimics the role of an enzyme active site by modulating access of the substrate to the Ir center. It is shown that the regioselectivity of the reaction arises from a complicated balance of the attractive and repulsive interactions between the substrate and ligand and their corresponding entropic penalties across the high-energy C–H activation and C–B bond formation transition states in the reaction pocket. We predict a trend of increasing para-selectivity with an increase in the size of the substrate substituent in the order SiH3 (and Me) < SiMe3 < Si(t-Bu)3, which is consistent with the experimentally observed trend. It is shown that an increase in the steric bulk of the ligand by introducing bulkier 3,5-substituents to the phenyl rings of the diarylphosphino groups of L1 decreases the para-selectivity. This computational prediction was validated by experiments on C–H borylation of trimethyl(phenyl)silane by using the 3,5-di-tert-butylphenyl analogue of MeO-BIPHEP (L3) as a diphosphine ligand that showed a decrease in para/meta ratio from 88:12 (L1) to 50:50 (L3). Combination of the presented computational and experimental results illustrates that the regioselectivity of the reaction is not fully governed by repulsive steric interactions but instead by a complex balance of steric and electronic interactions between the substrate and flexible reaction pocket. We expect that the provided detailed mechanistic study will greatly enhance our ability to design the next generation of ligands with increased para-selectivity and generality.

Related post

  1. CH Alkenylation of Azoles with E…
  2. カーボンナノリング:最短のカーボンナノチューブ
  3. Decarbonylative organoboron cros…
  4. Six-fold C–H Borylation of Hexa-…
  5. Nickel-Catalyzed Aromatic C–H Fu…
  6. Construction of Covalent Organic…
  7. Programmed Synthesis of Arylthia…
  8. Annulative π-Extension (APEX) of…

Twitter@Itami Lab

Itami Lab Facebook

Instagram@Itami Lab

This error message is only visible to WordPress admins

Error: API requests are being delayed. New posts will not be retrieved.

There may be an issue with the Instagram access token that you are using. Your server might also be unable to connect to Instagram at this time.

Error: API requests are being delayed for this account. New posts will not be retrieved.

There may be an issue with the Instagram access token that you are using. Your server might also be unable to connect to Instagram at this time.

Error: No posts found.

Make sure this account has posts available on instagram.com.

Click here to troubleshoot

最近の記事

Flickr@Itamilab

天池先輩からコーヒースープ伴夫妻からのお歳暮です!潤さん、宮村さん、ありがとうございます!!武藤さん、ビールありがとうございます!平賀大都わーいやなさん、あつしさん、ありがとうございます!!だいぶ前だけど、Stripes look #ootdHalloween lookラインを洗う時ですら格好良く。戸谷先生教育実習!imageけいしゅう、誕生日おめでとう!誕生日は英吉家!!3年生に名古屋ぼろ勝ちアピール中!!アリシア卒業おめでとう女子会!
PAGE TOP