Preparation of organomanganese reagents from organic halides with activated manganese

Reduction of Li2MnCl4 with magnesium metal provided activated manganese as a black suspension in THF. Treatment of organic halides such as allyl bromides, α-halo esters or aryl halides with activated manganese furnished various organomanganese reagents which reacted further with electrophiles to afford the corresponding adducts. The reaction of a ketone bearing an iodoaryl moiety with this active manganese induced cyclization to provide dihydroindene derivative.