R.E. Maleczka Jr. et al. / Tetrahedron 69 (2013) 4000e4008
4005
149.4; HRMS (EI) m/z 333.1245 [MꢁBu]þ; calcd for C14H29OSnþ
column chromatography [silica gel; hexanes/EtOAc 90/10] to afford
a partially separable mixture of the stannanes 28a and 28b
(894 mg, 88%).
333.1235.
4.1.5.10. Preparation of 26a/26b (Table 1, entry 10). Applying
conditions A to alkyne 10 (84 mg, 1 mmol) for 3 h afforded 26a and
26b (6:1). The reaction was cooled to room temperature, concen-
trated, and subjected to column chromatography [silica gel; 95/5
hexane/EtOAc, 1% TEA] to afford a separable mixture of the isomers
26a and 26b as clear oils (286 mg, 76%).
Applying conditions B to alkyne 10 (84 mg, 1 mmol) for 12 h
afforded 26a and 26b (2.3:1). The crude reaction was concentrated
and subjected to column chromatography [silica gel; 95/5 hexane/
EtOAc, 1% TEA] to afford a separable mixture of the isomers 26a and
26b as clear oils (293 mg, 78%). Spectroscopic data was consistent
with literature reports.8
Applying conditions D, alkyne 12 (285 mg, 1 mmol), hydroqui-
none (10 mg, 9 mol %), and MoBI3 (8.6 mg, 2 mol %) were dissolved in
THF (1 mL) in a pressure tube. The Bu3SnH (0.8 mL, 3 mmol) was
added to the solution dropwise. The tube was sealed and the solu-
tion was heated to 55 ꢀC to afford 28a and 28b (3.7:1). When com-
pleteas judged by TLC, the reactionwas cooled to roomtemperature,
concentrated, and subjected to column chromatography [silica gel;
90/10 hexane/EtOAc, 1% TEA] to afford a partially separable mixture
of the isomers 28a and 28b as clear oils (436 mg, 76%).
Data for 28a: IR (neat) 2956, 1700 cmꢁ1
;
1H NMR (500 MHz,
CDCl3) 0.02 (s, 6H), 0.81e0.94 (m, 21H), 1.22e1.35 (m, 10H),
d
1.42e1.55 (m,12H), 2.41 (q, J¼6.0 Hz, 2H), 3.58 (t, J¼6.0 Hz, 2H), 4.11
(q, J¼7.1 Hz, 2H), 6.00 (tt, J¼30.2, 7.1 Hz, 1H); 13C NMR (125 MHz,
4.1.5.11. Preparation of 27a/27b (Table 1, entry 11). Applying
conditions A to alkyne 11 (146 mg, 1 mmol) for 3 h afforded 27a and
27b (3.6:1). The reaction was cooled to room temperature, con-
centrated, and subjected to column chromatography [silica gel; 95/
5 hexane/EtOAc, 1% TEA] to afford a separable mixture of the iso-
mers 27a and 27b as clear oils (415 mg, 95%).
Applying conditions B to alkyne 11 (146 mg, 1 mmol) for 12 h
afforded 27a and 27b (2.8:1). The crude reaction was concentrated
and subjected to column chromatography [silica gel; 95/5 hexane/
EtOAc, 1% TEA] to afford a separable mixture of the isomers 27a and
27b as clear oils (431 mg, 99%). Spectroscopic data were consistent
with literature reports.1,2
CDCl3)
d
ꢁ5.3, 10.2, 13.7, 14.4, 18.3, 25.5, 25.9, 27.3, 28.9, 31.7, 32.4,
59.9, 63.0, 135.8, 153.3, 171.2; HRMS (EI) m/z 577.3092 [MþH]þ;
calcd for C27H57O3SiSnþ 577.3093.
Data for 28b: IR (neat) 2962, 1716 cmꢁ1 1H NMR (300 MHz,
;
CDCl3)
d 0.01 (s, 6H), 0.81e0.98 (m, 21H), 1.20e1.35 (m, 12H),
1.38e1.60 (m, 10H), 2.85 (t, J¼7.7 Hz, 2H), 3.59 (t, J¼6.3 Hz, 2H), 4.12
(q, J¼7.1 Hz, 2H), 5.90 (s, 1H); 13C NMR (125 MHz, CDCl3)
ꢁ5.3, 9.9,
d
13.7, 14.3, 18.3, 26.0, 27.5, 29.0, 30.6, 33.0, 35.1, 59.6, 63.1, 127.7,
164.2, 173.9; HRMS (ESI) m/z 577.3228 [MþH]þ; calcd for
C27H57O3SiSnþ 577.3093.
4.1.5.13. Preparation of 29a/29b (Table 2, entry 2). Silyl ether 12
(0.15 g, 0.53 mmol) was stirred in MeOH (1 mL) overnight with
Amberlyst-15 (0.15 g). The reaction mixture was filtered through
Celite, concentrated, and subjected to column chromatography [sil-
ica gel; hexanes/EtOAc 80/20] to afford 65 mg (72%) of the alcohol 13.
4.1.5.12. Preparation of 28a/28b (Table 2, entry 1). TBSCl (50.5 g,
335 mmol) was added in small portions to a 0 ꢀC solution of 5-
hexyn-1-ol (34.0 mL, 305 mmol) in CH2Cl2 (500 mL) containing
TEA (51.0 mL, 366 mmol) and DMAP (3.7 g, 30.5 mmol). The solu-
tion was stirred for 20 min and then allowed to warm to room
temperature while stirring. The reaction mixture was poured into
a saturated NH4Cl(aq) solution and the layers were separated. The
organic phase was washed with NH4Cl(aq) and the combined
aqueous layers were extracted with ether. The combined organics
were dried over MgSO4, filtered, and concentrated. The crude
product was subjected to column chromatography [silica gel; 90/10
hexane/EtOAc] to afford 64.3 g (100%) of tert-butyl(hex-5-ynyloxy)
dimethylsilane. Spectroscopic data were consistent with literature
reports.25
Data for 13: IR (neat) 3405, 1701 cmꢁ1
;
1H NMR (300 MHz,
CDCl3)
d 1.26 (m, 3H), 1.65 (m, 5H), 2.35 (m, 2H), 3.63 (m, 2H), 4.17
(q, J¼7.1 Hz, 2H); 13C NMR (75 MHz, CDCl3)
d 14.0, 18.4, 23.8, 31.6,
61.8, 62.0, 73.4, 88.9, 153.8.
Applying conditions C, alkyne 13 (2.00 g, 11.75 mmol), hydro-
quinone (118 mg, 9 mol %), and MoBI3 (100 mg, 2 mol %) were
dissolved in THF (11.75 mL) in a pressure tube. Bu3SnF (5.44 g,
17.6 mmol) was added to the solution followed by PMHS (1.05 mL,
17.6 mmol). The tube was sealed and the solution was heated to
55 ꢀC. The reaction was complete in 1 h and concentrated. The
crude product 29a and 29b (3.4:1) was purified by column chro-
matography [silica gel; hexanes/EtOAc 80/20] to afford the stan-
nanes 29a and 29b (3.50 g, 64%).
Applying conditions D, the alkyne 13 (170 mg, 1 mmol), hydro-
quinone (10 mg, 9 mol %), and MoBI3 (8.6 mg, 2 mol %) were dis-
solved inTHF (1 mL) in a pressure tube. The Bu3SnH (0.8 mL, 3 mmol)
was added to the solution dropwise. The tube was sealed and the
solution was heated to 55 ꢀC. When the reaction was judged com-
plete by TLC it was concentrated. The crude product 29a and 29b
(4.3:1) was purified by column chromatography [silica gel; hexanes/
EtOAc 80/20] to afford the stannanes 29a and 29b (423 mg, 92%).
Data for 29a: IR (neat) 3418, 2962,1714 cmꢁ1; 1H NMR (300 MHz,
A solution of n-BuLi (100 mL, 1.6 M in THF, 160 mmol) was added
to a ꢁ78 ꢀC THF (400 mL) solution of tert-butyl(hex-5-yn-1-yloxy)
dimethylsilane (28.32 g, 133.3 mmol) under N2. The resulting
mixture was stirred for 30 min. Ethyl chloroformate (15.3 mL,
160 mmol) was added. After stirring for 1 h at ꢁ78 ꢀC, the reaction
was quenched with saturated NH4Cl(aq) and extracted with EtOAc.
The combined organic layers were dried over MgSO4, filtered, and
concentrated to afford the crude product. Purification by column
chromatography [silica gel; hexanes/EtOAc 90/10] resulted in 46.3 g
(61% yield) of the ester 12. Spectroscopic data were consistent with
literature reports.25
Data for 12: IR (neat) 2238, 1717, 1076, 839 cmꢁ1
,
1H NMR
CDCl3) d 0.78e1.02 (m, 15H), 1.20e1.34 (m, 9H), 1.38e1.62 (m, 10H),
(300 MHz, CDCl3)
d
ꢁ0.01 (s, 6H), 0.85 (s, 9H), 1.26 (t, J¼7.1 Hz, 3H),
2.42 (q, J¼7.1 Hz, 2H), 3.54 (t, J¼6.6 Hz, 2H), 4.12 (q, J¼7.1 Hz, 2H),
1.60 (m, 4H), 2.33 (t, J¼6.8 Hz, 2H), 3.59 (t, J¼5.7 Hz, 2H), 4.17 (q,
5.96 (tt, J¼30.8, 7.1 Hz, 1H); 13C NMR (75 MHz, CDCl3)
d 10.2, 13.7,
J¼7.2 Hz, 2H). 13C NMR (75 MHz, CDCl3)
d
ꢁ5.4, 14.0, 18.3, 18.4, 24.1,
14.4, 25.3, 27.2, 28.9, 31.6, 32.1, 60.0, 62.5, 136.0, 153.1, 171.2; HRMS
25.9, 31.7, 61.7, 62.3, 73.2, 89.1, 153.8.
(ESI) m/z 463.2231 [MþH]þ; calcd for C21H43O3Snþ 463.2229.
Applying conditions C, alkyne 12 (500 mg, 1.76 mmol), hydro-
quinone (18 mg, 9 mol %), and MoBI3 (15.1 mg, 2 mol %) were
dissolved in THF (1.76 mL) in a pressure tube. Bu3SnF (817 mg,
2.64 mmol) was added to the solution followed by PMHS (0.16 mL,
2.64 mmol). The tube was sealed and the solution was heated to
55 ꢀC. The reaction was complete in 1 h and then concentrated
to afford 28a and 28b (3.3:1), which were then purified by
Data for 29b: IR (neat) 3455, 2956, 1714 cmꢁ1 1H NMR
;
(300 MHz, CDCl3) d 0.81e1.06 (m,15H),1.21e1.36 (m, 9H),1.40e1.53
(m, 8H), 1.54e1.65 (m, 2H), 1.91 (br s,1H), 2.83 (t, J¼7.7 Hz, 2H), 3.67
(q, J¼6.6 Hz, 2H), 4.12 (q, J¼7.1 Hz, 2H), 5.91 (t, J¼32.5 Hz, 1H); 13C
NMR (75 MHz, CDCl3)
d 9.8, 13.6, 14.3, 25.3, 27.3, 28.9, 32.1, 34.4,
59.7, 62.0, 127.7, 164.2, 174.3; HRMS (ESI) m/z 463.2233 [MþH]þ;
calcd for C21H43O3Snþ 463.2229.