Question 1 The scheme below depicts a sequence of reactions that makes extensive use of boron, silicon and organolithium chemistry. pin SiMe Ph Buli pinBSiMe Ph OH- OSIMe Bu -CbO Os/BuMe pinB1 Os/BuMez LICHCI OSIEts OH SiMe Ph Cb= HO. Osi BuMez - Osi BuMez os/BuMe (a) Suggest reagents and conditions to convert alcohol 1 into silylether 2 and provide a curved arrow mechanism for this reaction. [5 marks] (b) Explain why the organolithium base 'BuLi is capable of deprotonating the silylether 2 to give the anion 3. [2 marks] (c) Experimentally it was found that 'BuLi on its own produced very little of the anion 3. Suggest what could be added to this reaction to improve the yield of anion 3 and explain why this would help. [3 marks] (d) Suggest a curved arrow mechanism for the conversion of anion 3 to the disilane 4 which involves loss of Cboe as a leaving group. Your answer should comment on any key issues of stereoselectivity that arise. [5 marks] (e) Conversion of disilane 4 to the alkylborane 5 requires LiCH2Cl, explain why this reagent must be generated at low temperature and what its fate might be if it were warmed up. [2 marks]