No abstract

The treatment of silylethynyloxyarenes with allylic pivalates in the presence of a palladium catalyst led to efficient C-H bond cleavage in both substrates and a novel annulation reaction to give 2,3-bismethylenechromanes. When ortho-allylated silylethynyloxybenzenes were used as the substrates, the same products were obtained. This result shows that site-selective intramolecular hydrovinylation is involved in the annulation reaction. The synthetic utility of the products was demonstrated by the construction of condensed polycycles.

The treatment of silylethynyloxyarenes with allylic pivalates in the presence of apalladium catalyst led to efficient CÀHbond cleavage in both substrates and anovel annulation reaction to give 2,3-bismethylenechromanes.W hen orthoallylated silylethynyloxybenzenes were used as the substrates, the same products were obtained. This result shows that siteselective intramolecular hydrovinylation is involved in the annulation reaction. The synthetic utility of the products was demonstrated by the construction of condensed polycycles.

An intramolecular exo-hydroarylation of 2-aryloxy-1,4-disilylbut-1-en-3-ynes via ortho-C-H bond activation under palladium(0) and acid catalysis was found to give 2,3-bis(silylmethylidene)-2,3-dihydrobenzofurans. The two silyl groups present probably promoted the reaction and played a key role in stabilizing the diene moiety in the product. The products readily led to functionalized condensed cycles by a Diels-Alder reaction.

Emissive 2-Methylidene--2H-1,4-benzoxazin-3(4H)-ones. -(MINAMI*, Y.; KANDA, M.; SAKAI, M.; HIYAMA, T.; Tetrahedron 71 (2015) 26-27, 4522-4534, http://dx.