91Ó°ÊÓ

When lithium is used, the halogen and metal exchange to form the organolithium reagent and function as a nucleophilic agent and also as a base. They are stereospecific.

Organocuprate is used in many nucleophilic substitution reactions to get products such as aldehydes and ketones. They are stereospecific.

CBS is a chiral reducing agent. It is a boronic compound that functions as an asymmetric reduction and forms enantiomeric alcohols. They are stereospecific.

(S)-CBS reagent provides hydrides that can attack the carbonyl carbon center position from the front and yield alcohol having an R-configuration where the alcohol group lies in the ‘dash’ position.

Metal Hydrides such as ${\mathrm{LiAIH}}_4$are strong reducing agents which can reduce an aldehyde into primary alcohol and a ketone into secondary alcohol.