New synthesis of a seven member ring fused heterocycles using ring expansion reaction of an aromatic ring

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(1) Ketones reacted with magnesium bromide salt of trimethylsilyldiazomethane (TMSCHN_2) to give the corresponding 2-diazo-2-(trimethylsilyl)ethanols which were easily converted to pyraazoles by 1,3-dipole cycloaddition the reaction with acetylenes. (2) Aryl and heteroaryl aldehydes were easily converted to functionalized acetykenes in on-pot using lithium salt of TMSCHN_2. (3) TMSCHN_2 reacted with thiobenzoyl isocyanates to give the corresponding diazoketones which were converted to 2-azaazulenes by treatment with rhodium acetates. (4) Diazo(trimethylsilyl)methylmagnesium bromide smoothly reacted with t-butyl aryl(oxo)acetates to afford the corresponding arylpropiolates via alkylidenecarbene intermediates. (5) Diazo(trimethylsilyl)methylmagnesium bromide readily reacted with ketones and aldehydes to give 2-diazo-(2-trimethylsilyl)ethanoles which were efficiently converted to indazoles bearing a hydroxmethyl unit at 3-position by intermolecular [3+2]cycloaddition with benzynes. (6) Diazo(trimethylsilyl)methylmagnesium bromide reacted with (o-methoxyphenyl)(oxo)acetates to readily afford 2-unsubstituted benzofuran-3-carboxylates via oxonium ylides formed from the initially generated alkylidenecarbene intermediates. (7) Lithium trimethylsilyldiazomethane reacted with N-benzyl-β-aminoketones at -78℃in THF to give 3-substituted 1-benzyl-3-(trimethylsiloxy)pyrrolidines in moderate to good yields.