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Beauchamp Organic Reaction Review 1 Beauchamp Organic Reaction Review 1 Many of the reactions below have competing reactions. We mostly focus on the dominant reaction in a synthesis. That is what is shown in the small space available below. In a mechanism problem a more complete analysis is expected. You should be able to show the details of a mechanism when that is asked. In real reactions, specific recipes (solvent, temperature, concentration, etc.) are used. In these pages we only show typical results. Acid/Base reactions to make important reactants. – The pKa’s of the starting materials and the conjugate acids of the reagents are shown in parentheses. These reactions make essential strong base/nucleohiles. O O H NaOH NaNR2 N H N Na (pKa=9) (pKa=16) O (pKa=25) (pKa=37) Na O Beauchamp Organic Reaction Review 2 Free radical substitution reactions at sp3 C-H to make R-Br from alkanes. Br Br2 Br Br2 CH4 h H3C h Br Br Br2 Br2 h h Br Br Br2 Br2 h h Br Br2 Br Br2 h h Br 2 equivalents 2 equivalents Br Br Br2 Br2 Br h h Br Br 2 equivalents 2 equivalents Br Br Br2 Br2 h h E2 reactions to make alkenes (use one eq. potassium t-butoxide with RBr) and alkynes (use 3 eqs. sodium amide with RBr2, first two = E2, third equivalent = acid/base reaction) K Br K O O Br K K O O Br Br Br Br K K O O Beauchamp Organic Reaction Review 3 Br Br Br 1. excess NaNR2 H H 2. workup 1. excess NaNR2 2. workup Br H Br Br Br Br 1. excess NaNR2 H 2. workup 1. excess NaNR2 2. workup Free radical addition reactions of HBr to alkenes (makes anti-Markovnikov addition of HBr) HBr HBr ROOR Br ROOR Br h h HBr HBr ROOR Br ROOR Br h h Br Br HBr HBr ROOR ROOR h h Free radical substitution at allylic or benzylic sp3 C-H, synthesis of allylic or benzylic RBr Br Br2 h RBr + NaOH (= hydroxide) (SN2 at methyl and primary RBr, E2 > SN2 at secondary RBr and E2 at tertiary RBr, makes alcohols) OH Br Br NaOH OH NaOH H3C H3C S 2 S 2 > E2 N alcohol N alcohol OH OH Br Br NaOH minor NaOH E2 > S 2 major SN2 > E2 N alcohol Beauchamp Organic Reaction Review 4 Br OH Br NaOH NaOH SN2 > E2 alcohol only E2 alkene Br OH Br NaOH NaOH SN2 > E2 E2 > SN2 alkene (benzylic) alcohol Br Br OH NaOH OH NaOH SN2 > E2 alcohol SN2 > E2 (allylic) alcohol RBr + NaOR (= alkoxides) (SN2 at methyl and primary RBr, E2 > SN2 at secondary RBr and E2 at tertiary RBr, makes ethers) Br OR Br NaOR OR NaOR H3C H3C SN2 ether SN2 > E2 ether OR OR Br Br NaOR minor NaOR S 2 > E2 E2 > SN2 major N ether Br OR Br NaOR NaOR SN2 > E2 E2 > SN2 alkene (benzylic) ether Br Br OR NaOR OR NaOR SN2 > E2 SN2 > E2 ether (allylic) ether Beauchamp Organic Reaction Review 5 RBr + NaO2CR (=carboxylates) (SN2 at methyl, primary and secondary RBr, SN2, makes esters and E2 at tertiary RBr) O O Na O Na Br O Br O H3C O H3C O O SN2 ester SN2 > E2 ester O Br O Na Br O Na O O O O O ester SN2 > E2 SN2 > E2 ester Br O Na O Br O Na O O O SN2 > E2 ester only E2 alkene O Br O Na Br O Na O O O O O S 2 > E2 E2 > S 2 N N ester (benzylic) ester O Na O Na Br O Br O O O O S 2 > E2 O S 2 > E2 ester N N (allylic) ester Hydrolysis of esters, R’O2CR to make alcohols (acyl substitution reaction) Beauchamp Organic Reaction Review 6 RBr + NaOC(CH3)3 (t-butoxide) (SN2 at methyl and E2 at primary, secondary and tertiary RBr, makes alkenes) Br Br K K O O E2 alkene E2 alkene Br Br K K O O E2 alkene E2 alkene RBr + NaSH (monohydrogen sulfide) (SN2 at methyl, primary and secondary RBr, and E2 at tertiary RBr, makes thiols) Br SH Br SH NaSH NaSH H3C H3C SN2 S 2 thiol N thiol SH Br Br SH NaSH NaSH S 2 SN2 N thiol thiol Br SH Br NaSH NaSH SN2 SN2 thiol alkene Beauchamp Organic Reaction Review 7 Br SH Br SH NaSH NaSH SN2 SN2 thiol thiol Br SH Br SH NaSH NaSH S 2 N SN2 thiol thiol RBr + NaSR (= alkylthiolate) (SN2 at methyl, primary and secondary RBr, makes sulfides and E2 at tertiary RBr) Br SR Br SR NaSR NaSR H3C H3C SN2 SN2 sulfide sulfide SR Br Br SR NaSR NaSR S 2 SN2 N sulfide sulfide Br SR Br SR NaSR NaSR SN2 SN2 sulfide sulfide Br SR Br SR NaSR NaSR S 2 N sulfide SN2 sulfide + RBr + Na / imidate (1. SN2 at methyl, primary and secondary RBr, and E2 at tertiary RBr 2. NaOH (acyl substitution), makes 1o amine) Beauchamp Organic Reaction Review 8 RBr + 1. NaN3 (= azide = SN2 at carbon) 2. LiAlH4 (hydride = SN2 at nitrogen) 3. Workup (acid/base) (1. SN2 at methyl, 1o and 2o RBr, and E2 at 3o RBr, makes 1o amines) Br 1. NaN (S 2) 1. NaN3 (SN2) NH2 Br 3 N NH2 2. LiAlH (S 2) 2. LiAlH4 (SN2) H C 4 N H C 3 3. workup 3 3. workup o 1 amine 1o amine Br NH2 Br 1. NaN (S 2) NH2 3 N 1. NaN3 (SN2) 2. LiAlH (S 2) 4 N 2. LiAlH4 (SN2) 3. workup 3. workup 1o amine 1o amine Br NH2 Br 1. NaN3 (SN2) 1. NaN3 (E2) 2. LiAlH4 (SN2) 2. NA 3. workup 1o amine alkene Br NH2 Br NH 1. NaN3 (SN2) 2 1. NaN3 (SN2) 2. LiAlH4 (SN2) 2. LiAlH4 (SN2) 3. workup 3. workup 1o amine 1o amine Br NH2 Br 1. NaN (S 2) NH2 1. NaN3 (SN2) 3 N 2. LiAlH (S 2) 2. LiAlH4 (SN2) 4 N 3. workup 3. workup o 1 amine 1o amine o o o RBr + NaCN (= cyanide) (SN2 at methyl, 1 and 2 RBr, and E2 at 3 RBr, makes nitriles) Beauchamp Organic Reaction Review 9 o o o RBr + NaCCR (terminal acetylide) (SN2 at methyl and 1 RBr and E2 at 2 RBr and 3 RBr makes larger alkynes) Beauchamp Organic Reaction Review 10 + o o o RBr + Li / ketone enolate (SN2 at methyl, 1 and 2 RBr, and E2 at 3 RBr, makes larger ketones) + o o o RBr + Li / ester enolate (SN2 at methyl, 1 and 2 RBr, and E2 at 3 RBr, makes larger esters) new O Br O Li bond O Br O Li OR OR OR OR S 2 S 2 ester N ester N Beauchamp Organic Reaction Review 11 new Br O O Li bond Br O O Li OR OR OR OR ester SN2 SN2 ester + o o o RBr + Li / dithiane anion (SN2 at methyl, 1 and 2 RBr, and E2 at 3 RBr, makes aldehydes and ketones after hydrolysis with HgX2/H2O) Beauchamp Organic Reaction Review 12 o o o RBr + diphenylsulfide (SN2 at methyl, 1 and 2 RBr, and E2 at 3 RBr), makes sulfur salts that are used to make epoxides when reacted with 2. n-butyl lithium and 3. aldehydes and ketones S Br S Br Br Ph Br Ph Ph Ph Ph Ph S S S 2 S 2 N Ph N Ph Ph = phenyl Ph = phenyl sulfur salt for ylid sulfur salt for ylid Br S Br Ph Ph Br Ph Ph S S Ph Ph Ph Br SN2 S SN2 Ph = phenyl Ph sulfur salt for ylid Ph = phenyl sulfur salt for ylid S Br Ph S Br Br Br Ph Ph S Ph Ph Ph Ph S SN2 SN2 Ph = phenyl Ph = phenyl Ph sulfur salt for ylid sulfur salt for ylid o o o RBr + triphenylphosphine (SN2 at methyl, 1 and 2 RBr, and E2 at 3 RBr), make the phosphorous salts that are used to make the Z-alkenes when reacted with aldehydes and ketones. 2. n-butyl lithium and 3. aldehydes and ketones) Beauchamp Organic Reaction Review 13 Br P Br P Ph Br Ph Ph Ph Ph Ph Ph P Ph Ph Ph Br P SN2 Ph S 2 Ph N Ph = phenyl phosphorous salt for ylid Ph = phenyl phosphorous salt for ylid P Br Ph P Br Ph Br Br Ph Ph P Ph Ph Ph Ph Ph Ph P S 2 SN2 Ph N Ph Ph = phenyl phosphorous salt for ylid Ph = phenyl phosphorous salt for ylid RBr + lithium aluminum hydride (LiAlH4 = LAH) or deuteride (LiAlD4 = LAD) or sodium borohydride (NaBH4) or o o o deuteride (NaBD4) (SN2 at methyl, 1 and 2 RBr, and E2 at 3 RBr?) D LiAlD4 Br LiAlD4 Br or D or H C NaBD NaBD 3 4 H3C 4 SN2 SN2 Br LiAlD4 D Br LiAlD4 D or or NaBD4 NaBD4 SN2 SN2 Br D LiAlD4 D Br LiAlD4 or or NaBD4 NaBD4 SN2 SN2 Br LiAlD4 D Br LiAlD4 D or or NaBD4 NaBD4 SN2 SN2 Beauchamp Organic Reaction Review 14 o o o ROH + (HCl,HBr,HI or SOCl2, SOBr2 or PCl3, PBr3) (all are similar), SN2 at methyl, 1 ROH, and SN1 at 2 and 3 ROH , makes RX from alcohols HX HX or OH or Br OH Br SOX2 SOX2 H C 3 SN2 or H3C SN2 or PX3 PX3 X = Cl,Br X = Cl,Br HX HX OH or Br OH or Br SOX2 SOX2 SN1 or SN2 or PX3 PX3 X = Cl,Br X = Cl,Br OH HX Br OH HX Br or or SOX2 SOX S 2 2 N or SN1 or PX 3 PX3 X = Cl,Br X = Cl,Br HX OH HX Br Br OH or or SOX2 SOX2 SN1 or SN1 or PX3 PX3 X = Cl,Br X = Cl,Br HX HX OH or Br OH or Br SOX 2 SOX2 S 2 N or SN1 or PX 3 PX3 X = Cl,Br X = Cl,Br ROH + TsCl (makes tosylates = sulfur esters = good leaving group), Can follow this with 2.
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