BackPredict the product(s) that would result when the following molecules are allowed to react under the following conditions: (i) 1. BH3 2. NaOH, H2O2 (ii) 1. Hg(OAc)2 2. NaBH4 (iii) H2SO4 , H2O (iv) 1. OsO4 2. NaHSO3 (v) H2O (vi) NaOH, H2O . If there is no reaction, write 'no reaction.'
(d)
Predict the product(s) that would result when the following molecules are allowed to react under the following conditions: (i) 1. BH3 2. NaOH, H2O2. If there is no reaction, write 'no reaction.'
(a)
a. Show the reagents required to form the primary alcohol in each of the following reactions.
Identify A through O:
Hydroboration, an electrophilic addition reaction like those studied in Section 21.4, only gives 1,2-addition to buta-1,3-diene, regardless of temperature. Why?
Suggest an alkene to undergo hydroboration–oxidation (1. BH3 2. NaOH, H2O2) to give exclusively the alcohols shown. Pay close attention to the relative (but not absolute) stereochemical outcome.
(c)
Would you expect the following to produce an equal or unequal mixture of stereoisomers?
(c)
Suggest an alkene to undergo hydroboration–oxidation (1. BH3 2. NaOH, H2O2) to give exclusively the alcohols shown. Pay close attention to the relative (but not absolute) stereochemical outcome.
(b)
Suggest a reagent and a reactant that could be combined to make each of the following alcohols.
(a)
Predict the products you would get when the following alkenes undergo (i) hydroboration–oxidation (1. BH3 2. NaOH, H2O2 or (ii) oxymercuration–reduction [1. Hg(OAc)2, H2O 2. NaBH4].
(a)
Predict the product of each of the following hydroboration–oxidation or oxymercuration–reduction reactions used in the modern synthetic organic chemistry literature (modified to use reagents we are used to seeing).
(b) A two-step hydroboration–oxidation was used to prepare a silanediol peptidomimetic as a serine protease inhibitor (Org. Lett. 2012, 14, 4422–4425).
Predict the product of each of the following hydroboration–oxidation or oxymercuration–reduction reactions used in the modern synthetic organic chemistry literature (modified to use reagents we are used to seeing).
(c) A similar sequence was featured in the synthesis of muricadienin, a proposed precursor in the biosynthesis of solamin (Org. Lett. 2014, 16, 5886–5889).
a. Starting with 3-methyl-1-butyne, how can you prepare the following alcohols?
1. 2-methyl-2-butanol
b. In each case, a second alcohol would also be obtained. What alcohol would it be?
What stereoisomers are obtained from hydroboration–oxidation of the following compounds? Assign an R or S configuration to each asymmetric center.
a. cyclohexene
b. 1-ethylcyclohexene
Explain why 3-methylcyclohexene should not be used as the starting material in Problem 52b.