European Journal of Organic Chemistry
10.1002/ejoc.201601085
3H), 3.38 (s, 3H), 3.35 (s, 3H), 2.69 (m, 2H), 2.48 (m, 1H), 2.26 (m, 2H), 1.89 (m, 1H) ppm.
13C NMR (100 MHz, CDCl3): δ 195.5, 157.1, 146.0, 133.5, 129.3, 126.6, 123.8, 111.8, 108.3,
103.6, 101.8, 79.2, 64.4, 64.2, 56.1, 53.5, 52.8, 38.0, 36.0(4), 36.0(1) ppm. IR: νmax = 2937,
2887, 2829, 1682, 1573, 1475, 1439, 1272, 1245, 1017, 811, 729 cm–1. MS (ESI, +ve): m/z
(%) = 527 (100) [(M+Na)+]. HRMS (ESI, +ve): calcd for C20H25INaO7 [(M+Na)+] 527.0543;
found 527.0554.
rac-(4aS,9bS)-9b-(2,2-Dimethoxyethyl)-6-methoxy-4a,9b-dihydro-4H-spiro[dibenzo[b,d]
-furan-3,2'-[1,3]dioxolane]-9-carbaldehyde (10): A magnetically stirred and thoroughly
degassed solution of compound 9 (1.50 g, 2.97 mmol) in dry toluene (60 mL) maintained
under a nitrogen atmosphere was treated, sequentially, with Pd(OAc)2 (68 mg, 10 mol%),
dppp (251 mg, 20 mol%) and Ag2CO3 (2.40 g, 8.9 mmol). The resulting heterogeneous
mixture was heated at reflux for 4 h then cooled, filtered through a pad of diatomaceous earth
and the filtrate evaporated under reduced pressure. The residue thus obtained was subjected
to flash chromatography (silica, 9:1 v/v DCM/diethyl ether elution) to afford, after
concentration of the appropriate fractions (Rf = 0.7 in 9:1 v/v DCM/diethyl ether), compound
1
10 (1.00 g, 90%) as a white foam. H NMR (400 MHz, CDCl3): δ 9.84 (s, 1H), 7.36 (d, J =
8.4 Hz, 1H), 6.89 (d, J = 8.4 Hz, 1H), 6.52 (d, J = 10.3 Hz, 1H), 5.72 (d, J = 10.3 Hz, 1H),
5.23 (m, 1H), 4.32 (t, J = 5.2 Hz, 1H), 3.95 (m, 7H), 3.23 (s, 3H), 3.22 (s, 3H), 2.37–2.16
(complex m, 4H) ppm. 13C NMR (100 MHz, CDCl3): δ 190.9, 150.2, 148.3, 132.1, 131.5,
130.6, 127.7, 126.7, 110.4, 103.4, 102.7, 85.0, 64.9, 64.4, 56.0, 53.1, 53.0, 48.9, 39.8, 35.0
ppm. IR: νmax = 2934, 2888, 2836, 2730, 1686, 1607, 1570, 1283, 1117, 1045, 1013 cm–1. MS
(ESI, +ve): m/z (%) = 399 (100) [(M+Na)+]. HRMS (ESI, +ve): calcd for C20H24NaO7
[(M+Na)+] 399.1420; found 399.1422.
rac-1-((4aS,9bS)-9b-(2,2-Dimethoxyethyl)-6-methoxy-4a,9b-dihydro-4Hspiro[dibenzo-
[b,d]furan-3,2'-[1,3]dioxolan]-9-yl)-N-methylmethanamine (11): A magnetically stirred
solution of compound 10 (100 mg, 0.265 mmol), methylamine (0.2 mL of a 2 M solution in
THF, 0.4 mmol) and AcOH (0.1 mL) in dry DCM (2 mL) was treated with sodium
triacetoxyborohydride (85 mg, 0.4 mmol). The resulting mixture was maintained at room
temperature for 16 h then treated with NaHCO3 (5 mL of a saturated aqueous solution) and
extracted with DCM (3 x 5 mL). The combined organic phases were washed with brine (1 x
10 mL) before being dried (Na2SO4), filtered, and concentrated under reduced pressure. The
ensuing brown oil was subjected to flash chromatography (silica gel; 9:1 v/v
dichloromethane/methanol) to give, after concentration of the appropriate fractions (Rf = 0.2),
compound 11 (60 mg, 57%) as a pale-yellow oil. 1H NMR (400 MHz, CDCl3): δ 6.83 (d, J =
8.3 Hz, 1H), 6.72 (d, J = 8.3 Hz, 1H), 6.19 (d, J = 10.2 Hz, 1H), 5.75 (d, J = 10.2 Hz, 1H),
5.07 (m, 1H), 4.37 (t, J = 5.0 Hz, 1H), 4.31 (broad s, 1H), 3.96 (m, 4H), 3.84 (s, 3H), 3.77 (s,
2H), 3.24 (s, 3H), 3.21 (s, 3H), 2.46 (s, 3H), 2.24–2.03 (complex m, 4H) ppm. 13C NMR (100
MHz, CDCl3): δ 146.9, 144.7, 132.2, 130.3, 128.2, 126.8, 122.5, 111.5, 104.1, 102.0, 83.8,
64.7, 64.5, 55.8, 52.7, 52.6, 51.6, 49.3, 41.3, 35.3, 35.1 ppm. IR: νmax = 2954, 2934, 2891,
2835, 2789, 1621, 1581, 1506, 1428, 1277, 1203, 1116, 1046, 1014, 966, 948 cm–1. MS (ESI,
+ve): m/z (%) = 392 (100) [(M+H)+]. HRMS (ESI, +ve): calcd for C21H30NO6 [(M+H)+]
392.2073; found 392.2075.
Compound 12: A magnetically stirred solution of compound 10 (360 mg, 0.96 mmol) in
THF (20 mL) was treated with HCl (5 mL of a 1 M aqueous solution) then heated at reflux
for 2 h. The resulting mixture was cooled to room temperature then treated with NaHCO3 (20
mL of a saturated aqueous solution) and extracted with EtOAc (4 x 15 mL). The combined
organic phases were washed with brine (1 x 20 mL) before being dried (Na2SO4), filtered,
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