Premium
Rhodium‐Catalyzed Synthesis of Naphthalene Derivatives Through Cyclodimerization of Arylalkynes ☆
Author(s) -
Huang LingYu,
Aulwurm Uwe R.,
Heinemann Frank W.,
Kisch Horst
Publication year - 1998
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/(sici)1099-0682(199812)1998:12<1951::aid-ejic1951>3.0.co;2-b
Subject(s) - chemistry , naphthalene , catalysis , medicinal chemistry , azobenzene , rhodium , tris , hydrochloric acid , photochemistry , organic chemistry , molecule , biochemistry
RhCl(PPh 3 ) 3 in the presence of excess hydrochloric acid and azobenzene in refluxing 1‐pentanol catalyzes the cyclodimerization of arylalkynes to 1,2,3‐substituted naphthalene derivatives. This enables an easy access to 1,2,3‐triphenylnaphthalene ( 1 ), 7‐methoxy‐1,2,3‐tris( p ‐methoxyphenyl)naphthalene ( 2 ), 7‐methyl‐1,2,3‐tris( p ‐methylphenyl)naphthalene ( 3 ), and 7‐nitro‐3‐( p ‐nitrophenyl)‐1,2‐diphenylnaphthalene ( 4 ). A co‐cyclodimerization of tolan with 4‐octyne affords 3‐phenyl‐1,2‐dipropylnaphthalene ( 5 ). The structure of 4 was resolved by single‐crystal X‐ray structural analysis. The rate of formation of 1 is first‐order with respect to tolan and RhCl(PPh 3 ) 3 and exhibits activation parameters of Δ H ‡ = 94.7 ± 10 kJ mol −1 and Δ S ‡ = 36 ± 6 J K −1 mol −1 . Replacing HCl by HBr and HI decreases the rate by 28 and 55%, respectively. Although naphthalene formation occurs also in the absence of azobenzene, its presence stabilizes the catalyst, accelerates the reaction, and inhibits formation of 1‐chlorostilbene, which is the major by‐product. When RhCl(PCy 3 ) 2 is used as the catalyst, naphthalene formation even in the absence of azobenzene is highly selective, but proceeds much slower. No reaction is observed in non‐protic solvents.