Site-selective Pd-catalyzed coupling of 1,4-diiodo-1,3-alkadienes with Grignard reagents and its application to the synthesis of fulvenes.

[reaction: see text] The coupling reaction of 1,4-diiodo-1,3-alkadienes with a Grignard reagent in the presence of a catalytic amount of Pd(PPh3)4 proceeded with excellent site-selectivity. Synthetic application of the reaction was demonstrated by a regio- and stereoselective synthesis of 1,3,6-trisubstituted fulvenes.

Efficient and general synthetic method for preparing oligoenynes with either trans- or cis-olefinic configuration.

[reaction: see text] Efficient and practical synthesis of a variety of 1-iodo-4-trimethylsilylbut-1-en-3-yne derivatives with trans- and cis-olefinic configuration, and their repeated use as building blocks for the synthesis of trans- and cis-oligoenynes, respectively, are described.

Site-selective monotitanation of dialkynylpyridines and its application for preparation of highly fluorescent pi-conjugated oligomers.

Reaction of Ti(O-i-Pr)(4)/2i-PrMgCl reagent with 2,n-bis[(trimethylsilyl)ethynyl]pyridines, where n is 3, 4, 5, and 6, or with 3,4-bis[(trimethylsilyl)ethynyl]pyridines, proceeded with excellent site-selectivity to afford the corresponding monotitanated complex. Synthetic application of the reaction was demonstrated by an efficient preparation of pi-conjugated oligomers having pyridine and enyne units alternately, which possess intense blue fluorescence emission.

Synthesis of conjugated oligomers having aromatic and enediyne units alternately in the backbone that show intense fluorescence emission.

[structure: see text] Synthesis and fluorescence properties of pi-conjugated compounds having alternately an aromatic ring such as benzene, pyridine, and thiophene and an enediyne unit in the backbone are described.

Facile preparation of various heteroaromatic compounds via azatitanacyclopentadiene intermediates.

Coupling of acetylene, nitrile, and a titanium reagent, Ti(O-i-Pr)(4)/2 i-PrMgCl, generated new azatitanacyclopentadienes in a highly regioselective manner. Their subsequent reaction with sulfonylacetylene afforded pyridyltitanium compounds, which, upon reaction with electrophiles, gave substituted pyridines virtually as a single isomer. When optically active nitriles were used in this reaction, chiral pyridines were obtained without loss of the enantiopurity. Alternatively, the azatitanacyclopentadiene prepared from an unsymmetrical acetylene reacted with an aldehyde or another nitrile to give furans or pyrroles having four different substituents again in a regioselective manner.

One-pot synthesis of metalated pyridines from two acetylenes, a nitrile, and a titanium(II) alkoxide.

Four-component coupling process involving two acetylenes, a nitrile, and a divalent titanium alkoxide reagent, Ti(O-i-Pr)(4)/2i-PrMgCl, directly yielded titanated pyridines in a highly selective manner. The reaction can be classified into four categories: (i) a combination of an internal acetylene, a terminal acetylene, sulfonylnitrile, and the titanium reagent to yield alpha-titanated pyridines, (ii) a combination of an internal acetylene, a (sulfonylamino)acetylene, a nitrile, and the titanium reagent to yield alternative alpha-titanated pyridines, (iii) a combination of an internal acetylene, a (sulfonylamino)acetylene, a nitrile, and the titanium reagent to yield titanated aminopyridines, and (iv) a combination of an acetylenic amide, a terminal acetylene, a nitrile, and the titanium reagent to yield pyridineamides with their side chain titanated. Some of these reactions enabled virtually completely regioselective coupling of two different, unsymmetrical acetylenes and a nitrile to form a single pyridine. Synthetic applications of these reactions have been illustrated in the preparation of optically active pyridines and medicinally useful compounds.

Site-selective iodine-magnesium exchange reaction of 1,4-diiodo-1,3-alkadienes by an organomagnesium ate complex, and its application to synthesis of polysubstituted styrenes and phenols.

When 1,4-diiodo-1,3-alkadienes were treated with i-PrBu2MgLi, highly site-selective iodine-magnesium exchange reaction took place to afford, after the reaction with electrophiles, a variety of 1-iodo-1,3-alkadiene derivatives. Synthetic utility of the reaction was demonstrated by an efficient preparation of polysubstituted styrenes and phenols.

Efficient and practical method for synthesizing optically active indan-2-ols by the Ti(O-i-Pr)(4)/2 i-PrMgCl-mediated metalative Reppe reaction.

An efficient and practical synthesis of optically active indan-2-ols 1 has been developed starting from readily accessible optically active 4-siloxy-1,6-alkadiynes 2 and ethynyl p-tolyl sulfone, where the metalative Reppe reaction mediated by an economical divalent titanium reagent, Ti(O-i-Pr)(4)/2 i-PrMgCl, is a key step.

Highly practical and general synthesis of monodisperse linear pi-conjugated oligoenynes and oligoenediynes with either trans- or cis-olefin configuration.

Efficient and practical synthesis of a variety of 1-iodo-4-(trimethylsilyl)but-1-en-3-yne derivatives 1 and 2 with trans- and cis-olefin configuration was described. Their repeated use as building blocks allowed the facile synthesis of trans- and cis-oligoenynes, respectively. Development of a highly practical method for preparing monodisperse trans- and cis-oligoenediynes having the effective conjugation length was also accomplished by using 5 and 4, which can be readily prepared from 1 and 2, respectively.