Pyridine durch Cyano-[4+2]-Cycloaddition

New reactions of 3,4‐dihydro‐6,7‐dimethoxyisoquinoline ylide with nitrile derivatives

“…Our proposed mechanism for the α‐amino‐nitrile formation can be seen in Scheme 7. The chemistry of ethyl cyanoformate is well explored, there are reports describing the use of the reagent as a dienophile [11] or a dipolarophile [12] in cycloadditions (which was originally our targeted reactivity), but it can also be used for example, for the dehydration of aldoximes to the corresponding nitriles [13]. Otherwise, this ester is potentially capable of reacting with nucleophiles at either the sp 2 carbon providing derivatives of formic esters (acting as an acyl transfer reagent) or the sp hybridized C‐atom to become an in situ source of cyanide ion.…”

“…Our proposed mechanism for the α-amino-nitrile formation can be seen in Scheme 7. The chemistry of ethyl cyanoformate is well explored, there are reports describing the use of the reagent as a dienophile [11] or a dipolarophile [12] in cycloadditions (which was originally…”

Nickel-Catalyzed Dehydrogenative [4 + 2] Cycloaddition of 1,3-Dienes with Nitriles

“…Potentially, the [4 + 2] cycloaddition of 1,3-butadienes with nitriles followed by aromatization would be an efficient method for the regioselective construction of the pyridine skeleton. However, because the elaborate diene, which has a leaving group (X) in its structure, is required to give the pyridine framework by elimination of HX from the corresponding primary product, 2,5-dihydropyridine, only scattered examples have been reported so far. , Otherwise, either a very high reaction temperature or a highly activated nitrile such as perfluoroalkyl nitrile is required. Furthermore, no catalytic dehydrogenative [4 + 2] cycloaddition reaction of butadienes with nitriles has been reported yet (eq 2) …”