Reaction Products and Reagents (Su

Ketone + NaBH4

50:50

Cram chelation

• heteroatom on α position

• chelating metal (Mg)

New group adds to least sterically hindered side on chelated transition state

Felkin-Anh (no heteroatom)

• No α position heteroatom

• Conformation is fixed by bulky Ph group

Felkin-Anh (with heteroatom):

• Cl in α position

• No chelating metal (Na⁺ non-chelating)

• Conformational fix from most electronegative atom favouring 90^o to the C=O 

+ (S)-CBS catalyst

+ BH₃

• Transition state conformational fix from bulky group orientation on the 6 membered ring (structure not to be memorised)

• (S) catalyst adds H to the front (when the larger group is drawn on the left) 

(or R-SH)

• SN2 mechanism so inversion of stereochemistry

• Sulfonate is a good leaving group so promotes this reaction (wouldnt react with unadapted alcohol precursor)

+ LDA

+ Et-I

• 50:50

+ LDA

+ Et-I

• New group adds opposite side to ⁱPr (when drawn this way)

• Li chelates the enolate oxygen and carbonyl

• Enolate favours cis

What reagents to produce:

• OH protection method

• OH deprotection

• Amine deprotection