Mikio Hori

Radical C-Se bond cleavage of selenonium salts with grignard reagents or magnesium metal

Abstract The reaction of 2-methylisoselenochromanium salt with Grignard reagents afforded the reductive ring-opened product by the single electron transfer (SET) mechanism, not by the self-decomposition of σ-selenurane. The same reduction was observed in the reaction of the selenonium salt with magnesium metal. Some other selenonium salts were easily reduced by magnesium metal to give ring-opened products.

Vinyl radical generation with selenoborane and its application to cyclization reaction of enynes

Abstract Tris(methylseleno)- and tris(phenylseleno)boranes added to acetylenes to afford methylseleno- and phenylseleno-substituted Z -vinylselenides in high yields. The addition reactions proceeded by way of free radicals and were applied to cyclization reactions of enyne compounds. The radical cyclization provided pyrrolidine derivatives diastereoselectively.

Novel synthesis of medium-sized heterocycles containing a sulfur or selenium atom

Abstract Medium-sized sulfur- or selenium-containing heterocyclic compounds were synthesized by the reductive cross-piece bond cleavage of bicyclic sulfonium and selenonium salts bearing a bridgehead sulfur or selenium atom with magnesium metal or sodium borohydride.

Reduction of sulfonium and selenonium salts with samarium diiodide

Abstract Treatment of sulfonium and selenonium salts with 2 equiv of a THF solution of samarium diiodide caused the reductive cleavage of the C-S or C-Se bonds in high yields. The bond cleavage took place regioselectively between the positive sulfur or selenium atom and the carbon atom with an electron-withdrawing group or a vinyl group. Some medium-sized cyclic sulfides or selenides were synthesized by this method.

Endo selective cyclizations of selenonium ion intermediate : efficient formation of 1-halo-3-seleno-cyclohexanes

Selenoacetal 1 was cyclized with tin(IV) chloride in the 6-Endo-Trig mode to give 1-chloro-3-methylselenocyclohexanes (2a,b), regio- and stereoselectively. Bromo- or iodocyclohexane derivatives were afforded by use of tin(IV) bromide or titanium(IV) iodide, respectively.

A polar cycloaddition of 2-thianaphthylium ions with 1,3-dienes and some properties of the cycloadducts

2-Thianaphthylium ions (1) underwent a polar cycloaddition with 1,3-dienes to afford benzo-fused bicyclic sulfonium salts (2) bearing sulfur atom at bridge-head in excellent yields. The cycloadducts underwent retro-addition reaction to generate the cation (1), which was easily trapped with other diene. Reaction of the adduct (2d) with several nucleophiles caused the ring-opening of (2d) to afford 1-allyl (6) and 1-homoallyl substituted 2-thiochromenes (7) in good yields.

THERMAL REARRANGEMENT OF 9-BENZYL-10-AZA-9-THIAPHENANTHRENES

Abstract 9-Benzyl-10-aza-9-thiaphenanthrenes ( 3 ) generated from 9-benzyl-10-aza-9-thiaphenanthreniun salts ( 2 ) by treatment with base underwent thermal 1,2-benzyl migration to give the corresponding 6-benzyl-6H-dibenzo[c,e][1,2]thiazines ( 4 ).

Thermolysis of [1,2,4]triazolo[1,5-a]pyrimidine n-ylides

Abstract 5,7-Dimethyl[1,2,4]triazolo[1,5-a]pyrimidinio-3-phenacylide ( 3 ) generated by the reaction of an iminium salt ( 2 ) with 1 eq. of triethylamine, underwent a new thermal ring cleavage of the triazole moiety to give the pyrimidine derivative. However reaction of 2 with 2 eq. of triethylamine afforded the 2-iminooxazoline derivative. The iminooxazoline reacted with nucleophiles such as alcohols or amines to give imidazoles.

Reactions of azathiabenzene anion with electrophiles. Formation and x-ray analysis of novel heterocyclic compounds from the reaction with carboxylic ester

Abstract The anion (2) generated from 9-methyl-10-aza-9-thiaphenanthrene (1) reacted with carboxylic ester to give the spiro compounds (9a), (9b) via Sommelet-Hauser rearrangement, whose structures have been confirmed by an X-ray crystal structure determination of (9a).

Ylide-induced ylide formation: A novel double cycloaddition reaction of A [1, 2, 4]triazolo [1, 5-a]pyrimidinum ylides

Abstract Treatment of 5, 7-dimethyl-3-phenacyl[1, 2, 4]triazolo[1, 5- a ]pyrimidinium ylide ( 2 ) with methyl propiolate leads to a novel double cycloaddition and resulted in the formation of 3,9-dihydropyrazolo[1,5- c ]pyrimidine derivative ( 4 ).