The oxidant iodosobenzene diacetate was combined with the cheap,environment-friendly FeCl3 as a chloride source to produce an efficient chlorinating agent for α-chlorination of ketene dithioacetals through direct C(sp2)-H chlorination.Furthermore,the synthetic utility of α-chlorinated ketene dithioacetals was verified by the intermolecular cyclization with hydrazine hydrate,leading to the synthesis of pyrazoles,in which a 1,2-sulfur migration was involved.
A green and efficient synthesis of 3-pyrazolyl indoles was developed by the eye 1 ocondensation reactionof β-ethylthio-β-indolyl-α,β-unsaturated ketones with semi carbazide hydrochloride as hydrazine equivalent in thepresence of 3 equiv. of PEG400(la/PEG mole ratio of 1:3) in reflux water. This procedure did not require toxichydrazine and product purification, eliminating the use of toxic liquid chemicals.
