For the reaction shown below (a) provide the structure of the major product (b) and a reasonable mechanism for its formation. CH3 Hg(OAc)2, H2SO4 (aq), H3C

3. (1) Propose each of the following syntheses (show suitable reagents for each step). OEt ماده EtO H

A8

2. a) Provide the missing reaction product(s), or conditions to the following reactions. ACO + hv DCM, -55 °C NaOH (aq) C11 H1602

Answer ALL parts. (a) Treatment of enone C with tetrabutylammonium fluoride leads to the formation of heterocycle D. 2 steps BU4NF C9H1602 A + B D OSIME,tBu (i) Enone C can be prepared from alkyne A and aldehyde B in two steps via a gold-catalysed reaction. Identify A and B and provide reagents/conditions for a synthesis of C. (ii) Give the structure of D and classify the ring-closing reaction for its formation from C according to Baldwin's rules (iii) Sketch the key molecular orbitals involved in the ring-closing reaction in part (ii) and hence explain whether the reaction is favourable or unfavourable.

Hh.182.

Draw the organic products formed in each of the following reactions. (i). (ii) (iii) (iv) (v) CI +:C=C-H + H₂O CH₂C=CCH₂CH3 HgSO4, H₂SO4 Na, NH3 2 equiv Br₂ (1) Sia₂BH.THF (2) H₂O₂ NaOH

1) Provide an arow-pushing mechanism for the reaction shown below. 8 H3O+ (aq)

(a) (b) (c) (d) Where products are missing, provide the structure of the major elimination product expected. Where the product is shown, draw the structure of the missing starting substrate necessary to complete each transformation. In all cases, show stereochemistry of the product clearly. CI ONa CI tok -OK Br OTS DBU DBU major alkene minor alkene major alkene minor alkene major alkene minor alkene major alkene minor alkene

3. Outline a synthetic scheme for the preparation of the compounds A from the suggested starting material by the suggested method. Make sure to clearly indicate all reagents needed to perform each step of the synthetic scheme. (a) OH O=S=O Br A (b) H₂N. (c) HO3S. Br Br A A 1 Br