Navigation

0 Hits

  • Previous / Next

You are using Science Of Synthesis as a Guest.
Please login to access the full content or check if you have access via
2.4.1.1.1.3 Using In Situ Prepared Dialkoxyboranes

DOI: 10.1055/sos-SD-208-00321

Murata, M.Science of Synthesis: Cross Coupling and Heck-Type Reactions, (20132458.

Neopentylglycolborane (52), which can be conveniently prepared in situ from 2,2-dimethylpropane-1,3-diol (neopentylglycol) and borane–dimethyl sulfide complex, is found to be an effective boron source in the nickel-catalyzed coupling of aryl—X electrophiles 53 (Scheme 12). The borylation in the presence of a suitable nickel catalyst and 3 equivalents of anhydrous triethylamine in toluene affords the corresponding neopentylglycol boronates 54 in high yields. The use of [1,1′-bis(diphenylphosphino)ferrocene]dichloropalladium(II) with in situ prepared 52 is ineffective due to poisoning of the palladium catalyst in the presence of dimethyl sulfide from borane–dimethyl sulfide complex. The combination of 10 mol% of [1,3-bis(diphenylphosphino)propane]dichloronickel(II) and 10 mol% of 1,3-bis(diphenylphosphino)propane was originally used as a catalyst system, but this catalyst has a limited substrate scope as only less hindered aryl iodides and bromides {e.g., 53 [X = I; Ar1 = 4-MeO2C(CH2)2C6H4]} are efficiently converted into 54.[‌58‌] The mixed ligand system comprising 5 mol% of [1,3-bis(diphenylphosphino)propane]dichloronickel(II) and 10 mol% of 1,1′-bis(diphenylphosphino)ferrocene greatly improves the substrate scope, and is particularly recommended for ortho-substituted substrates [e.g., 53 (X = Br; Ar1 = 2-F3CC6H4)][‌59‌] and aryl chlorides [e.g., 53 (X = Cl; Ar1 = 4-NCC6H4)].[‌60‌] In addition, zinc powder, which acts as a reducing agent for the nickel(II) precursor, considerably accelerates the reaction,[‌61‌] and achieves the borylation of aryl methanesulfonates or 4-toluenesulfonates [e.g., 53 (X = OTs; Ar1 = 3-MeO2CC6H4)].[‌62‌] These improved conditions tolerate ester, ketone, and nitrile functionalities, but do not tolerate pyridine moieties and aldehyde carbonyl groups.

Meeeee 88 Meeeeeeeee ee Meee—M Meeeeeeeeeeee eeee Me Meee Meeeeeee Meeeeeeeeeeeeeeeeeeee[‌88‌‌88‌]

Meeeeeeeeee 88

Me8 M Meeeeeeeee Meeee (%) Mee
8-MeM8M(MM8)8M8M8 M MeMe8(eeee),e eeee, 8 e 88 [‌88‌]
8-MeMM8M8 Me MeMe8(eeee),e eeee, 88 e 88 [‌88‌]
8-M8MM8M8 Me MeMe8(eeee), eeee, 88 e 88 [‌88‌]
8-M8MM8M8 Me MeMe8(eeee), eeee, Me,e 8 e 88 [‌88‌]
8-MeM8M8 Me MeMe8(eeee), eeee, 8.8 e 88 [‌88‌]
8-MMM8M8 Me MeMe8(eeee), eeee, 88 e 88 [‌88‌]
8-MMM8M8 Me MeMe8(eeee), eeee, Me,e 8 e 88 [‌88‌]
8-MMM8M8 MMe MeMe8(eeee), eeee, Me,e 8 e 88 [‌88‌]
8-MeM8MM8M8 MMe MeMe8(eeee), eeee, Me,e 8 e 88 [‌88‌]

e 88 eee% ee MeMe8(eeee) eee eeee.

e Mee eeeeeeee eee eeeeeeeee ee eee eeeeeeee ee Me eeeeee (8 eeeee).

Meeeeeeeeeee Meeeeeeee

8-Meee-8,8-eeeeeeee-8,8,8-eeeeeeeeeeeeee 88; Meeeeee Meeeeeeee:[‌88‌]

MMMMMMM: M eeeeeeeeeee eeeeee ee eeeeeeee ee eeeeeeeee eeeeee eee eeeeeeeeeee ee 8,8-eeeeeeee-8,8,8-eeeeeeeeeeeee. Meeeee–eeeeeeee eeeeeee eeeeeee eee 8,8-eeeeeeee-8,8,8-eeeeeeeeeeeee eeeeee eeeeeeee ee eeeeeee eeee eeeee.

M eeee ee 8,8-eeeeeeee-8,8,8-eeeeeeeeeeeee (88) eee eeeeeeee ee eeeeeee: Me e eeeeee eeee ee eeeeeeeeeeeeeee (88.8 eeee) ee eeeee eeeeeee (8 eM) eee eeeeee eeeee MMM (88.8 eeee). Meeee 88 eee ee eeeeeeee ee 8 °M, eee eeeeeee eee eeeeeee ee eeee ee 88 °M eee eeee eeeeeeee ee 88 °M eeeee eee eeeeeeeee eee eeeeee. Mee eeeeeeeee eeee eee eeee eeeeeeee ee eee eeee eeee eeeeeee eeeeeee eeeeeeeeeeee.

M eeeeeeee eeeee eeeeeee eeee e eeeeeeee eeeeeee eee, MeMe8(eeee) (8.8 eeee), eeee (8.8 eeee), eee eee eeee eeeeeeee 88 (M = Me; 8.8 eeee) eee eeeeeeeee eee eeeeee eeee M8 (eeeee eeeeee). Meeeeee (8 eM), eeeee Me8M (88.8 eeee), eee eee eeeee eeee ee 8,8-eeeeeeee-8,8,8-eeeeeeeeeeeee (88) eeee eeeee eee eeeeeee, eee eee eeeeeeeee eeeeeee eee eeeeee ee 888 °M eeee eeeeeeee. Meeee eee eeeeeeee eee eeeeeeee (eeeeeeeee ee MM eeeeeeee), eee eeeeeeee eee eeeeeeee eee eeee eeeeeeee ee eee. ee MM8Me (88 eM). Mee eeeeeee eeeee eee eeeeee eeee eee. ee MM8Me (8 × 88 eM) eee eee eeeeeeee eeeeee eeee eeeeeeeee eeee MeMMe (88 eM). Mee eeeeeeee eeeeeee eeeeeeee eeee eeeee (MeMM8) eee eee eeeeeee eee eeeeeee. Mee eeeee eeeeeee eee eeeeeeee ee eeeeee eeeeeeeeeeeeee (eeeeee eee) ee eeeeeeeeeeeeeeeee ee eeeee eee eeeeeeeeeeee eeee eeeeeee.

References


Cookie-Einstellungen