Hirokazu Maeda

Ene reaction of α-thiocarbocation: Simple synthesis of E,E-2,4-alkadienoic esters from 1-alkenes

Abstract Pummerer reaction intermediate 2 of α-methylsulfinylacetate ( 1 ) has been found to react with 1-alkenes to afford ene adducts 3 . E,E-2,4-decadienoic ester ( 5 ) was synthesized from the adduct 3 (n=5).

Acid-catalyzed cyclizations of n-vinyl-α-sulfinylacetamides A novel synthetic approach to erythrinane

Abstract Under the Pummerer reaction conditions, N-(1-cyclohexenyl)-N-methyl-α-(methylsulfinyl)acetamide ( 7a ) cyclized in a 5-endo trigonal fashion through the intermediary cation ( 8 ) to give the tetrahydro-4H-oxindole ( 10 ). The reaction was successively applied to a novel synthesis of erythrinane skeleton.

Cationic polar cycloaddition with chloromethyl phenyl sulfides

Chloromethyl phenyl sulfides 3 underwent [4+ +2] type polar cyclo-additions with styrene, trans-stilbene, and phenylacetylene in the presence of stannic chloride to afford the thiochroman 4, 5 and thiochromen derivatives 6. Under the same reaction conditions, N-allyl-α-chloro-α-(phenylthio)acetamide (7) gave the intramolecular cycloaddition product 8.

Pummerer reaction intermediate as an initiating function for cationic olefin cyclization

Abstract Treatment of N-(2-methyl-2-propenyl)-N-methyl-α-(methylsulfinyl)acetamide ( 6a ) with trifluoroacetic anhydride caused the cationic olefin cyclization through a Pummerer reaction intermediate to give the six-membered lactams 7 and 8 . Similar reaction converted N-2-butenyl-N-methyl-a-(methylsulfinyl)acetamide ( 6b ) to the five-membered lactam 9 , and N-2-propenyl-N-methyl-α-(methylsulfinyl)- acetamide ( 6c ) to the five-membered lactams 11 and 12 .

Synthesis of N-cyano monoaza crown ethers

Abstract N-Cyano monoaza crown ethers were prepared by the reaction of cyanamide with oligoethylene glycol dichlorides or ditosylates in the NaH/DMSO reaction system and led to the derivatives.

Strong base induced cycloaddition of 3-carboxy-1-methylindole-2-acetic anhydride and 2-carboxybenzo[b]furan-3-acetic anhydride: synthesis of polycyclic peri-hydroxylated indole and benzofuran compounds

Abstract Generation of indole- and benzofuran-2,3-orthoquinodimethane-like intermediates is described. The cycloaddition reaction of these intermediates to dienophiles provided an efficient one-pot synthesis of polycyclic perihydroxylated indole and benzofuran compounds.

Intramolecular cyclization of N,N-di(oligooxyethylene)amines: A new synthesis of monoaza crown ethers

Abstract The reaction of N,N-di(oligooxyethylene)amines with arenesulfonyl chloride in the presence of alkali metal hydroxide was investigate. It was found that the monoarenesulfonates of N,N-di(oligooxyethylene)amines were first formed as intermediates, and their subsequent intramolecular cyclization gave N-unsubstituted monoaza crown ethers rather selectively.

Facile synthesis of monoaza crown ethers

A facile one-step synthesis of monoaza crown ethers by treatment of dialkanolamines with oligothylene glycol di(toluene-p-sulphonates) or dichlorides in ButOM–ButOH (M = Na, K) is described.