Bromination of Tetralin
1793
135 m g, 14%), an d 1,2,4-tribromo-1,2,3,4-tetrahydronaphthalene (6; 140 m g, 5%) were eluted
successively. Recrystallisation of 6 from h exan e gave n eedle-like colourless crystals, m .p.
59–60 °C. 1H NMR (CDCl3): 2.85 (dtd, J(3a,3b) = 14.5, J(3b,2) = J(3b,4) = 6.2, J(3b,1) = 1.4, 1 H,
H3b); 3.30 (ddd, J(3a,3b) = 14.5, J(3a,4) = 9.6, J(3a,2) = 2.8, 1 H, H3a); 4.82 (m , 1 H, H2);
5.55 (dd, J(3b,1) = 1.4, J(1,2) = 2.9, 1 H, H1); 5.63 (dd, J(4,3a) = 9.6, J(4,3b) = 6.2, 1 H, H4);
7.26–7.66 (m , 4 H, aryl). 13C NMR (CDCl3): 40.2 (t), 47.2 (d), 52.1 (d), 52.8 (d), 130.9 (d),
131.5 (d), 132.9 (d), 133.1 (d), 135.2 (s), 136.6 (s). For C10H9Br3 (369) calculated: 32.56% C,
2.46% H; foun d: 31.97% C, 2.68% H.
Th en , elution of th e colum n with ch loroform gave 2-bromo-1,2,3,4-tetrahydronaphthalen-
1-ol (5; 140 m g, 8%), colourless crystals, m .p. 111–112 °C (ch loroform ) (ref.12 110 °C). 1H
NMR (CDCl3): 2.28 an d 2.51 (AB, J(3a,3b) = 13.7, 2 H, H3a an d H3b); 2.60 (s, OH); 3.00 (m ,
2 H, H4a an d H4b); 4.35 (ddd, J(2,3a) = 3.3, J(2,3b) = 9.5, J(1,2) = 7.0, 1 H, H2); 4.91 (d,
J(1,2) = 7.0, 1 H, H1); 7.60, 7.35 an d 7.14 (m ′s, 4 H, aryl). 13C NMR (CDCl3): 28.4 (t), 30.0
(t), 56.5 (d), 74.4 (d), 127.0 (d), 128.3 (d), 128.5 (d), 128.8 (d), 135.2 (s), 135.7 (s). For
C
10H11BrO (227) calculated: 52.89% C, 4.88% H; foun d: 52.67% C, 4.81% H. 1,4-Dibrom o-
1,2,3,4-tetrah ydron aph th alen e h as been prepared previously by th e reaction of
1,2,3,4-tetrah ydron aph th alen e with N-brom osuccin im ide, as reported by Djerassi11, but th e
exact stereoch em istry of th e product (cis or trans) h as n ot been determ in ed13. On th e oth er
h an d, Bloun t14 reported form ation of 1,2-dibrom o-1,2,3,4-tetrah ydron aph th alen e in about
30% yield on brom in ation of 1,2,3,4-tetrah ydron aph th alen e with brom in e with out solven t
at 95 °C. Th e differen ce presum ably arises as a result of en h an ced elim in ation of HBr from
1-brom o-1,2,3,4-tetrah ydron aph th alen e in Bloun t’s h otter an d m ore con cen trated con di-
tion s, followed by addition of brom in e to th e 1,2-dih ydron aph th alen e th us form ed.
Brom in ation of 1,2-Dih ydron aph th alen e
A solution of 1,2-dih ydron aph th alen e (8; 130 m g, 1.00 m m ol) in CHCl3 (3 m l) was treated
with brom in e (176 m g, 1.1 m m ol). After rem oval of th e solven t in vacuo, recrystallisation of
th e residue from CH2Cl2–petroleum eth er afforded trans-1,2-dibromo-1,2,3,4-tetrahydro-
naphthalene (9; 261 m g, 95%), m .p. 66 °C (ref.15 70 °C). 1H NMR (CDCl3): 7.13–7.36 (m , 4 H,
aryl H′s); 5.68 (t, 1 H, J(1,2) = J(1,3) = 1.5); 4.94–4.98 (m , 1 H); 3.20–3.30 (m , 1 H); 2.75–3.01
(m , 2 H); 2.14–2.29 (m , 1 H). 13C NMR (CDCl3): 136.5 (s), 134.9 (s), 133.3 (d), 131.2 (d),
130.9 (d), 128.7 (d), 79.7 (d), 79.1 (d), 78.4 (d), 53.6 (d), 27.2 (t), 26.5 (t).
Ph otobrom in ation of 1,2-Dibrom o-1,2,3,4-tetrah ydron aph th alen e
To a solution of 1,2-dibrom o-1,2,3,4-tetrah ydron aph th alen e (9; 145 m g, 0.50 m m ol) in
CDCl3 (0.5 m l) in an NMR tube brom in e (0.88 g, 0.55 m m ol) was added. Th e m ixture was
irradiated by a projector lam p (150 W) for 15 m in . HBr gas was rigorously evacuated durin g
th e reaction . Th e residue obtain ed after rem oval of th e solven t was recrystallised from
CH2Cl2–petroleum eth er to give 1,2,4-tribromo-1,2,3,4-tetrahydronaphthalene (6; 156 m g,
85%).
Hydrolysis of 1,2-Dibrom otetralin (9)
A solution of 1,2-dibrom o-1,2,3,4-tetrah ydron aph th alen e (9; 145 m g, 0.50 m m ol) in CHCl3
(20 m l) was m ixed with silica gel 60 (20 g) an d H2O (0.5 m l). Th e resultin g m ixture was
stirred for 2 days. Th e solution was filtered an d th e solven t was rem oved in vacuo. Th e resi-
Collect. Czech. Chem. Commun. (Vol. 65) (2000)