1,3-Dipolar cycloadditions of 2-thio-3-chloroacrylamides with diazoalkanes

Abstract

2-Thio-3-chloroacrylamides undergo 1,3-dipolar cycloadditions with diazoalkanes leading to a series of novel pyrazolines and pyrazoles. The mechanistic and synthetic features of the cycloadditions to the 2-thio-3-chloroacrylamides at both the sulfide and sulfoxide levels of oxidation are rationalised on the basis of the nature of the substituents.

The influence of reaction conditions on the Diels–Alder cycloadditions of 2-thio-3-chloroacrylamides; investigation of thermal, catalytic and microwave conditions

“…A similar effect was seen in earlier studies on 1,3-dipolar cycloadditions with the β-chloroacrylamides. 16 Interestingly, the isolated yields of 12a and 12b were lower from the cycloaddition of 3a and 3n than from the cycloaddition of the corresponding benzylsulfinyl derivatives 3u and 3p (entries 1 and 2, Table 3 vs. entries 3 and 5, Table 3), presumably associated with the more facile elimination during the cycloaddition.…”

“…15 The employment of -chloroacrylamides as dipolarophiles in 1,3-dipolar cycloadditions has also been reported recently. 16,17 The -chloroacrylamides are a highly functionalized group of unsaturated compounds, and the range of substituents which can be incorporated on the basic acrylamide framework is substantial. 14,18 These derivatives are potential dienophiles leading to novel cycloadducts in reactions with dienes.…”

Diastereoselective sulfur oxidation of 2-thio-3-chloroacrylamides

“…While the diastereomeric ratios achieved are modest, the resulting sulfoxides have significant synthetic potential, for example as Michael acceptors, dienophiles or dipolarophiles. 27,28 Results and Discussion…”

1,3-Dipolar cycloadditions of 2-thio-3-chloroacrylamides with nitrile oxides and nitrones

“…Notably, cycloadditions with diazoalkanes require longer reaction times to go to completion. 16 On reaction of the sulfoxides 6−9 (entries 1−4, Table 1) and 11 (entry 7, Table 1) and the sulfide 15 (entry 9, Table 1) with benzonitrile oxide 4, a precipitate formed as the reaction progressed and the isoxazoline cycloadducts 18-21, 24…”