Synthesis of Silaphenalenes by Ruthenium‐Catalyzed Annulation between 1‐Naphthylsilanes and Internal Alkynes through CH Bond Cleavage

Abstract

Ruthenium-catalyzed annulation of 1-naphthylsilanes with internal alkynes afforded silaphenalenes through cleavage of the C-H bond at the 8-position of the naphthalene. [RuH2 (CO){P(p-FC6 H4 )3 }3 ] efficiently catalyzed the reaction. The use of 1-naphthyldiphenylsilane as a substrate resulted in a better yield of the annulation product compared to the use of silanes with alkyl groups on the silicon atom. Internal alkynes with both aryl and alkyl groups were tolerated in this reaction.

Synthesis and Characterization of (Di)Benzosilaphenalenes

“…Diisopropylsilylanthracene (1c), however, was recovered after being subjected to the annulation conditions. Considering 1-diisopropylsilylnaphthalene gave the annulation product in the previous work (44% isolated yield), 9 it appears that the bulky 9-anthryl group may partially disturb the annulation without affecting the CH cleavage process. Diphenylacetylenes with isopropoxy groups (2c) and with trifluoromethyl groups (2d) at the parapositions were also effective as the annulation partners of silylanthracene 1.…”

“…Ruthenium-catalyzed annulation of hydrosilylnaphthalenes with internal alkynes afforded 1-sila-1H-phenalene in good yield. 9 Moreover, the annulation could result in the addition of bulky regions to the substrate. Bulkiness around the chromophore is an important factor to obtain solid-state emission of organic molecules.…”

“…The reactivity of 1a was higher than that of 1-dimethylsilylnaphthalene under conditions similar to those mentioned in the previous report (59% GC yield). 9 The high reactivity of 1a could be related to two-fold peri-positions, which increases the probability of activation of an active CH bond by the ruthenium catalyst. The diethylsilyl group (1b) and diphenylsilyl group (1d) were also tolerated in the annulation.…”

Regioselective C−H Functionalization of Naphthalenes: Reactivity and Mechanistic Insights

“…Similarly to 1‐naphthols, 1‐hydrosilyl naphthalenes were used as substrates to realize direct C8‐functionalization. In 2015, Tokoro and Fukuzawa's group reported a ruthenium‐catalyzed annulation reaction between 1‐naphthylsilanes 36 and internal alkynes to deliver interesting silaphenalenes 37 (Scheme ) . The catalytic cycle, supported by DFT calculations, proposed first an oxidative addition of Ru 0 , generated by the reduction of Ru II with the alkyne, into hydrosilane followed by the alkyne insertion leading to intermediate IV .…”

Recent Advances in Ruthenium(II)‐Catalyzed C−H Bond Activation and Alkyne Annulation Reactions

“…The presence of a phenyl group on the silicon atom, such as 1‐naphthyldiphenylsilane, resulted in a better yield of the silaphenalenes compared to those with the use of silanes with alkyl groups on the silicon atom. The reaction tolerates internal alkynes with both aryl and alkyl groups as well as electron‐donating and electron‐withdrawing substituents …”