Terminal alkynes from aldehydes via dehydrohalogenation of (Z)-1-iodo-1-alkenes with TBAF

Terminal alkynes were prepared in near quantitative yields via dehydrohalogenation of (Z)-1-iodo-1-alkenes with tetrabutylammonium fluoride (TBAF) under mild conditions. The methodology was expanded to include a one-pot, direct synthesis of terminal alkynes from aldehydes without the necessity of isolating and purifying the intermediate iodoalkene.     

Synthesis of functionalized iodoalkenes using a multicomponent reaction triggered by electrophilic iodination of alkenyldiazoacetates

Diazo compounds are frequently used as precursors of metal carbenoids and act as soft nucleophiles even without the use of metal catalysts. The resulting diazonium species may also be trapped by various nucleophiles. The introduction of an iodine functionality applicable for the coupling reaction into an alkenyl diazo compound, however, has not been reported. We developed iodoalkoxylation reactions of alkenyl diazoacetates using an electrophilic iodinating reagent and oxygen nucleophile. This catalyst-free multicomponent reaction proceeded regioselectively, furnishing trisubstituted vinyl iodides in 31%–71% yield. The synthesized iodoalkenes were converted into the corresponding olefins with various functionalities in good yield via Suzuki-Miyaura coupling reactions with arylboronic acids under palladium catalysis to demonstrate the synthetic utility of the developed reaction sequence.     

Highly regioselective hydroiodination of terminal alkynes and silylalkynes with iodine and phosphorus reagents leading to internal iodoalkenes

Markovnikov-type hydroiodination of terminal alkynes with iodine and Ph₂P(O)H took place selectively to afford the corresponding internal iodoalkenes in good yields. Combination of (PhO)₂P(O)H and Ph₂P(O)OH instead of Ph₂P(O)H also provided internal iodoalkenes in excellent yields. This hydroiodination is advantageous in terms of mild conditions, convenient operation, and tolerance to various functional groups. In addition, direct synthesis of internal iodoalkenes from silylalkynes was also achieved by using a mixed system of iodine and phosphorus reagents.     

Palladium-catalysed aminocarbonylation of iodoarenes and iodoalkenes with aminophosphonate as N-nucleophile

The high-yielding synthesis of novel N-acyl phosphonates with unprecedented structure was carried out by a homogeneous carbonylation reaction under mild reaction conditions. The palladium-catalysed aminocarbonylation of iodoalkenes (1-iodo-cyclohexene, 1-iodo-4-tert-butyl-cyclohexene, 1-iodo-2-methyl-cyclohexene and α-iodostyrene) with diethyl α-aminobenzyl-phosphonate as N-nucleophile resulted in the exclusive formation of carboxamides. The same reaction with iodoaromatics (iodobenzene, 2-iodothiophene) provided the corresponding carboxamide in high yields and some 2-keto-carboxamides as side products due to single and double carbon monoxide insertion, respectively.