A kinetic study on the intramolecular direct radical substitution reaction on tin atoms was undertaken.

Controlling the reactivity of the nitrogen or oxygen nucleophile of an amide group to form C–N or C–O bonds by tuning reaction conditions is one of the most challenging issues in the use of amides in organic synthesis. Both nucleophiles in the amide group can individually participate in reactions, and most reactions employ a substrate-controlled methodology to achieve selectivity. However, in the reaction of α-bromoamides and acrylates, we successfully controlled the reactivity of the nitrogen or oxygen nucleophile of the amide group to afford a lactam via carboamidation or an iminolactone via carbooxygenation, using a copper catalyst system with an appropriate base.

Optically active ent-calystegine B4 was prepared in 13 steps from commercially available chiral L-dimethyl tartrate. The synthesis was achieved by the Michael addition and the aldol reaction of nitromethane to form cycloheptanone in a stereoselective manner. Reduction of the nitro group in the presence of Boc(2)O accomplished an efficient conversion to amino cycloheptanone, which readily afforded the desired ent-calystegine B4.

A one-step conversion of allylic nitro compounds to substituted 2,3-dihydrofurans has been developed. Allylic nitro compounds, which are readily available from nitroalkenes and formaldehyde, underwent a double allylic substitution reaction catalyzed by a palladium complex to give 2,3-dihydrofurans in good yield.

Bicyclic dihydrothiophenes are readily prepared by a radical cascade cyclization reaction triggered by the addition of a thiyl radical under thermal or photoirradiation conditions. The translocated radical attacks the sulfur atom in the initial radical donor unit in an SHi manner. Sufficient stereoselectivity is achieved when a large excess of disulfide is used for the reaction under photoirradiation conditions. The reaction in the absence of solvents provides vinylsulfides instead of dihydrothiophenes. Thus, the sulfur atom in the thiyl radical serves as a sulfur biradical synthetic equivalent.

SummaryBicyclodihydrosiloles were readily prepared from optically active enyne compounds by a radical cascade reaction triggered by tris(trimethylsilyl)silane ((Me3Si)3SiH). The reaction was initiated by the addition of a silyl radical to an α,β-unsaturated ester, forming an α-carbonyl radical that underwent radical cyclization to a terminal alkyne unit. The resulting vinyl radical attacked the silicon atom in an SHi manner to give dihydrosilole. The reaction preferentially formed trans isomers of bicyclosiloles with an approximately 7:3 to 9:1 selectivity.

Dibutylmethyltin hydride and tert‐butyldibutyltin hydride were employed to examine radical cascade reaction of aza‐1,6‐enyne for the preliminary estimation of homofugality between alkyl groups by product distribution analysis. Use of either dibutylmethyltin hydride or tert‐butyldibutyltin hydride preferentially produced butylmethylstannolane, in which butyl group was mainly substituted by vinyl radical.

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