Organotin(IV)-Catalyzed Synthesis of Functionalized Dioxadisilacyclohexanes
FULL PAPER
chloromethane, and the combined organic extracts were washed with
water and saturated NaCl solution. After drying over MgSO4, the di-
chloromethane was removed by distillation at ambient pressure. For puri-
fication, the crude silanes were distilled under reduced pressure.
803 (m), 741 (m), 690 (m), 673 (m), 634 (w), 619 (w), 595 cmÀ1 (w); FAB-
MS: m/z (%): 675.2 [M+H+] (16.4); elemental analysis: calcd (%) for
C22H52O4Si2Sn2 (674.25): C 39.19, H 7.77, Si 8.33, Sn 35.21; found: C
38.91, H 7.58, Si 8.29, Sn 35.3.
General procedure D for the synthesis of 2,2,5,5-functionalized 1,4-dioxa-
2,5-disilacyclohexanes: (Acetoxymethyl)silanes were distilled prior to
cyclization reactions, to purities of at least 99.8% (as determined by GC
analysis) and stored over molecular sieves (4 ꢃ). Dioctyltin oxide
(0.5 mol%) was suspended in the appropriate silane, and the mixture was
heated at 120–1258C. Evolving alkyl esters were removed by distillation
under vacuum. The pressure was continuously decreased over a period of
approximately 6 h. After complete removal of the alkyl esters, the dioxa-
disilacyclohexanes were distilled from the reaction mixture.
(Chloromethyl)(diisopropoxy)methylsilane
(6c):
Dry
isopropanol
(32.0 mL, 422 mmol) was added to solution of imidazole (30.7 g,
a
452 mmol) and 4-(dimethylamino)pyridine (2.4 g, 20 mmol) in dry di-
chloromethane (350 mL). The solution was cooled to 08C. At that tem-
perature, dichloro(chloromethyl)methylsilane (32.1 g, 196 mmol) was
added dropwise, which resulted in precipitation of imidazole hydrochlor-
ide. The suspension was allowed to warm to room temperature and stir-
red overnight (12 h). After filtration, ammonium chloride solution (10%
in water, 200 mL) was slowly added. The organic phase was separated,
the aqueous layer was extracted with dichloromethane (2ꢄ75 mL), and
the combined organic extracts were washed with water (100 mL) and sat-
(Acetoxymethyl)methoxydimethylsilane (2): General procedure B, silane
1 (101 g, 731 mmol), potassium acetate (84.6 g, 862 mmol), tetrabutyl-
phosphonium bromide (4.96 g, 14.6 mmol), Hydroseal G 400 H (100 mL),
1108C, 5 h. Distillation at 928C (100 mbar) afforded 2 as a colorless
liquid (105 g, 648 mmol, 89%); 1H NMR (500 MHz, C6D6): d=3.80 (s,
AHCTUNGTREuGNUNN rated NaCl solution (100 mL), dried over MgSO4, and concentrated
under reduced pressure. Compound 6c (39.1 g, 186 mmol, 95%) was ob-
tained as a colorless liquid by distillation under reduced pressure; b.p.
708C (20 mbar); 1H NMR (500 MHz, C6D6): d=4.03 (sept, 3J
ACHTUNGTRENNUNG
À
À
2H; Si CH2 O), 3.24 (s, 3H; OCH3), 1.68 (s, 3H; Ac CH3), 0.07 ppm (s,
6.1 Hz, 2H; iPr CH), 2.62 (s, 2H; Si CH2 O), 1.11 (d, 3J
AHCTUNGTRENNUNG
13
À
À
À
À
6H; Si CH3); C NMR (126 MHz, C6D6): d=170.7 (C=O), 56.3 (Si
18H; iPr CH3), 0.23 ppm (s, 3H; Si CH3); 13C NMR (126 MHz, C6D6):
CH2 O), 50.4 (OCH3), 20.3 (Ac CH3), À3.7 ppm (Si CH3); 29Si NMR
À
À
À
(99 MHz, C6D6): d=À12.4 ppm; MS (70 eV): m/z (%): 146.9 [M+ CH3]
À
À
À
d=65.74 (iPr CH), 27.9 (Si CH2 O), 25.8 (iPr CH3), À5.2 ppm (Si
CH3); 29Si NMR (99 MHz, C6D6): d=À19.0 ppm; MS (70 eV): m/z (%):
209.0 [M+ÀH] (3.1); elemental analysis: calcd (%) for C8H19ClO2Si
(210.08): C 45.59, H 9.09, Si 13.32; found: C 45.25, H 9.29, Si 13.25.
À
(38.4); elemental analysis: calcd (%) for C6H14O3Si (162.07): C 44.41, H
8.70, Si 17.31; found: C 44.95, H 8.77, Si 17.23.
2,2,5,5-Tetramethyl-1,4-dioxa-2,5-disilacyclohexane (3): General proce-
dure D, dioctyltin oxide (965 mg, 2.67 mmol), silane 2 (86.7 g, 534 mmol),
1208C (pressure was decreased from 650 to 100 mbar). Silane 3 (40.6 g,
(Acetoxymethyl)dimethoxymethylsilane (7a): General procedure B, po-
tassium acetate (64.4 g, 656 mmol), tetrabutylphosphonium bromide
(3.85 g, 11.1 mmol), silane 6a (86.0 g, 556 mmol), diphenyl ether
(100 mL), 1108C, 8 h. After distillation, silane 7a was obtained as a color-
less liquid (89.4 g, 501 mmol, 90%); b.p. 708C (20 mbar); 1H NMR
230 mmol, 86%) was obtained as a colorless liquid by distillation at 428C
1
À
(12 mbar); m.p. 19–218C; H NMR (500 MHz, C6D6): d=3.51 (s, 4H; Si
CH2 O), 0.10 ppm (s, 12H; Si CH3); 13C NMR (126 MHz, C6D6): d=
À
À
56.8 (Si CH2 O), À3.1 ppm (Si CH3); 29Si NMR (99 MHz, C6D6): d=
9.1 ppm; MS (70 eV): m/z (%): 176.2 [M+] (92.9); elemental analysis:
calcd (%) for C6H16O2Si2 (176.07): C 40.86, H 9.14, Si 31.85; found: C
40.61, H 9.12, Si 31.56.
À
À
(500 MHz, C6D6): d=3.85 (s, 2H; Si CH2 O), 3.33 (s, 6H; OCH3), 1.68
À
À
À
(s, 3H; Ac CH3), 0.14 ppm (s, 3H; Si CH3); 13C NMR (126 MHz, C6D6):
À
À
À
d=170.7 (C=O), 53.7 (Si CH2 O), 50.2 (OCH3), 20.2 (Ac CH3),
À6.1 ppm (Si CH3); 29Si NMR (99 MHz, C6D6): d=À11.2 ppm; MS
À
(70 eV): m/z (%): 177.7 [M+] (1.2); elemental analysis: calcd (%) for
C6H14O4Si (178.07): C 40.43, H 7.92, Si 15.76; found: C 40.27, H 7.54, Si
15.63.
NMR data for the intermediate polymer in the formation of 3: 1H NMR
À
À
À
À
(300/500 MHz, C6D6): d=4.1–3.9 (Si CH2 OAc), 3.6–3.0 ([Si CH2 O]x,
OCH3), 1.86–1.82 ppm (Ac CH3); 1H NMR (300/500 MHz, CDCl3): d=
À
À
À
À
(Acetoxymethyl)diethoxymethylsilane (7b): General procedure A, potas-
sium acetate (56.7 g, 578 mmol), tetrabutylphosphonium bromide (3.32 g,
9.80 mmol), silane 6b (89.5 g, 490 mmol), 1108C, 8 h. Silane 7b (90.1 g,
3.77–3.67 (Si CH2 OAc), 3.46–3.37 (OCH3), 3.37–3.16 ([Si CH2 O]x),
2.03 ppm (Ac CH3).
2,2,5,5,8,8-Hexamethyl-1,4,7-trioxa-2,5,8-trisilacyclononane (4): Occasion-
ally contained as an “impurity” in silane
437 mmol, 89%) was obtained by distillation at 778C (16 mbar) as a col-
3
(see text); 1H NMR
1
À
À
orless liquid; H NMR (500 MHz, C6D6): d=3.90 (s, 2H; Si CH2 O),
3.66 (q, JACTHUNGTRENNNUG
À
À
À
(300 MHz, C6D6): d=3.34 (s, 18H; Si CH2 O), 0.15 ppm (s, 6H; Si
3
3
CH3); MS (70 eV): m/z (%): 264.1 [M+] (2.3).
(H,H)=7.0 Hz, 6H; Et CH3), 0.20 ppm (s, 3H; Si CH3); 13C NMR
À
2,2,7,7-Tetrabutyl-4,4,9,9-tetramethyl-1,3,6,8-tetraoxa-4,9-disila-2,7-distan-
nacyclodecane (5): Dibutyltin oxide (9.8 g, 39.4 mmol), silane 3 (3.5 g,
19.8 mmol), and toluene (5 mL) were heated to reflux (120–1258C, com-
plete dissolution) for some hours until 1H NMR monitoring showed that
the signals of the starting materials had disappeared and only product
signals were present. The mixture was first cooled to room temperature
and then in a refrigerator overnight. The white precipitate was separated,
washed with pentane, and dried in vacuo. Compound 5 (9.7 g, 14.4 mmol,
73%) was obtained as a white microcrystalline powder, which was mod-
erately soluble in tetrahydrofuran or toluene. From the mother liquor, no
further product could be obtained; m.p.: 98–1008C; 1H NMR (300 MHz,
À
À
(126 MHz, C6D6): d=170.7 (C=O), 58.6 (Et CH2), 54.3 (Si CH2 O), 20.3
(Ac CH3), 18.6 (Et CH3), À5.1 ppm (Si CH3); 29Si NMR (99 MHz,
À
C6D6): d=À15.0 ppm; MS (70 eV): m/z (%): 206.1 [M+] (0.4); elemental
analysis: calcd (%) for C8H18O4Si (206.10): C 46.57, H 8.79, Si 13.61;
found: C 46.43, H 8.90, Si 13.47.
(Acetoxymethyl)diisopropoxymethylsilane (7c): General procedure C,
potassium acetate (22.0 g, 224 mmol), tetrabutylphosphonium bromide
(1.31 g, 3.80 mmol), silane 6c (40.0 g, 190 mmol), 1108C, 6 h. Purification
by distillation provided 7c (41.0 g, 175 mmol, 92%) as a colorless liquid;
b.p. 70 8C (6 mbar); 1H NMR (500 MHz, C6D6): d=4.07 (sept, 3J
ACHTUNGTRENNUNG(H,H)=
À
À
C6D6): d=3.13 (s, 1J
A
(H,Sn)=35.7 Hz, 4H; Si CH2 O),
6.1 Hz, 2H; iPr CH), 3.90 (s, 2H; Si CH2 O), 1.71 (s, 3H; Ac CH3), 1.12
À
À
(d, 3J
E
À
3
1.91 (m, J
(H,Sn)=95.4 Hz, 8H; nBu CH2), 1.55 (m, 8H; nBu CH2), 1.45
13
À
(t, 3J
1J(H,C)=125.8 Hz, 12H; nBu CH3), 0.37 ppm (s, 1J
(H,Si)=6.4 Hz, 12H; Si CH3); C NMR (75 MHz, C6D6): d=55.2 (Si
(H,H)=7.6, 2J
(H,Sn)=70 Hz, 8H; Sn CH2), 1.08 (t, 3J
ACHTUNGTRENUN(NG H,H)=7.3,
C NMR (126 MHz, C6D6): d=170.6 (C=O), 65.5 (iPr CH), 54.9 (Si
À
CH2 O), 25.8 (iPr CH3), 20.4 (Ac CH3), À4.1 ppm (Si CH3); 29Si NMR
(99 MHz, C6D6): d=À17.9 ppm; MS (70 eV): m/z (%): 234.0 [M+] (0.2);
elemental analysis: calcd (%) for C10H22O4Si (234.13): C 51.25, H 9.46, Si
11.98; found: C 51.40, H 9.26, Si 12.16.
À
À
E
ACHTUNGTRENNUNG
13
À
À
ACHTUNGTRENNUNG
CH2 O), 28.1 ( JACHTUNGTRENNUNG ACHTNUGTRENNUNG
(C,Sn)=34 Hz; nBu CH2), 27.5 (3J
(C,Sn)=79 (117Sn)
2
À
and 82 Hz (119Sn); nBu CH2), 21.1 (1J(C,Sn)=598 (117Sn) and 623 Hz
AHCTUNGTERNNUNG
119
1
À
À
2,5-Dimethoxy-2,5-dimethyl-1,4-dioxa-2,5-disilacyclohexane (8a): Gener-
al procedure D, dioctyltin oxide (200 mg, 0.553 mmol), silane 7a (19.7 g,
111 mmol), 1208C (pressure was decreased from 650 to 20 mbar). The
crude product was distilled at 368C (2ꢄ10À1 mbar) to provide 8a (9.83 g,
47.2 mmol, 85%) as a colorless liquid; 1H NMR (500 MHz, C6D6): d=
(
Sn); Sn CH2), 14.3 (nBu CH3), 1.8 ppm ( J
G
29Si NMR (60 MHz, C6D6): d=0.01 ppm (2J
A
(112 MHz, C6D6): d=À141.8 ppm (br (Dn1/2 =70 Hz), 1J
(Sn,C)=616, 3J-
ACHTUNGTRENNUNG
3
(C,Sn)=85, J
N
sh), 2870 (m), 2857 (s), 2798 (m), 2725 (vw), 1464 (m), 1456 (m), 1423
(w), 1375 (w), 1341 (vw), 1285 (vw), 1261 (vw, sh), 1244 (s), 1207 (w),
1194 (vw), 1155 (w), 1075 (w), 982 (s), 926 (s), 883 (m), 869 (m), 824 (s),
À
À
3.69 (m, 4H; Si CH2 O), 3.51 and 3.35 (s, 6H; OCH3), 0.08 and
0.00 ppm (s, 6H; Si CH3); 13C NMR (126 MHz, C6D6): d=54.9 and 54.4
À
Chem. Eur. J. 2013, 19, 4818 – 4825
ꢂ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
4823