Rhodium-Catalyzed Cross-Coupling of Organoboron Compounds with Vinyl Acetate
作者:Jung-Yi Yu、Ryoichi Kuwano
DOI:10.1002/anie.200903146
日期:2009.9.14
A new coupling partner: Vinylacetate couples with organoboroncompounds in the presence of a rhodium catalyst; carbon–carbon bond formation occurs on the vinylic carbon attached to the acetoxy group. Conventional nickel and palladium catalysts were found to be ineffective for the reaction.
The reaction of cis and rans 2-iodomethyl 1-tosyloxycyclohexanes and 4-enes with nBuLi was studied and found to be stereospecific, the products being respectively bicyclo(4.1.0)hexane (ene) cis and methylene cyclohexane (ène). A parallel is drawn between this reaction and alkaline deshydrohalogenation of cyclic 1,2-halohydrins; a reaction pathway is proposed.
A process produces an aromatic compound by bringing an aromatic compound (B) into contact with molecular oxygen (C) in the presence of a catalyst (A) comprising at least one of (A1) a heteropolyacid and/or a salt thereof, and (A2) a mixture of oxoacids and/or salts thereof containing, as a whole, one of P and Si and at least one selected from V, Mo and W to thereby yield another aromatic compound (G) than the aromatic compound (B). The process can produce, for example, a corresponding aromatic hydroxy compound (G1) by allowing the aromatic compound (B) to react with the molecular oxygen (C) further in the presence of a reducing agent (D).
A novel and facile synthesis of 5-hydroxy-4-hydroxymethyl-2-cyclohexenylguanine 1 is described. The key steps involve a Diels-Alder reaction of ethyl (2E)-3-acetyloxy-2-propenoate 2 as dienophile with Danishefsky's diene 3 to build up the six-membered ring skeleton, a Fraser-Reid reductive rearrangement of the adduct using LiAlH(4), and base-moiety introduction using a Mitsunobu reaction. Optically
Tandem Cycloaddition Chemistry of Nitroalkenes: Preparative and Theoretical Studies on the Stereochemical Course of [3 + 2] Cycloaddition of Cyclic Nitronates
作者:Scott E. Denmark、Mark Seierstad、B. Herbert
DOI:10.1021/jo9818374
日期:1999.2.1
Intermolecular [3 + 2] cycloadditions between two cyclic nitronates and a series of dipolarophiles are examined. High facial selectivity is observed in all cases and is analyzed with the aid of ab initio transition structure calculations. Monosubstituted dipolarophiles reacted with exclusive regiocontrol. Disubstituted dipolarophiles reacted with varying degrees of regiocontrol, which was dependent