In:
Chemistry – A European Journal, Wiley, Vol. 24, No. 72 ( 2018-12-20), p. 19361-19367
Abstract:
A 2‐alkenoylpyridine‐bound N , N ′‐dioxide–Tb III complex has been found to absorb visible light to reach the excited state, leading to the direct visible‐light‐excited catalytic enantioselective [2+2] cycloaddition of 2‐alkenoylpyridines to various alkenes in the absence of an additional photosensitizer. Diverse enantioenriched cyclobutanes were successfully obtained (yields up to 70 %, 〉 19:1 d.r., 92 % ee ). The new chiral terbium(III) complex features a bathochromic shift, lower excitation energy, and facile intersystem crossing due to paramagnetic and heavy‐atom effects, which enable the antenna 2‐alkenoylpyridines to be excited. For comparison, a chiral N , N′ ‐dioxide–Sc III complex in combination with [Ru(bpy) 3 ]Cl 2 was efficient in the enantioselective photocycloaddition reactions of 2′‐hydroxychalcones with alkenes, thereby revealing that both substrates and metal salts have significant effects on the reaction.
Type of Medium:
Online Resource
ISSN:
0947-6539
,
1521-3765
DOI:
10.1002/chem.201804600
Language:
English
Publisher:
Wiley
Publication Date:
2018
detail.hit.zdb_id:
1478547-X
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