2.2 Synthesis of the methylsilatrane: (1R,2S)-1',6,6-trimethyl-spiro$\lbrack$bicyclo$\lbrack$3.1.1$\rbrack$heptane-2,3'-5-aza-2,8,9-trioxa-1-silabicyclo$\lbrack$3.3.3$\rbrack$undecane$\rbrack$

A mixture of trichloro-methylsilane (374mg, 2.5mmol), acetic anhydride (776mg, 7.8mmol) and NaOAc (50mg, 0.6mmol) was kept at 60$^{\circ}$C for 4h. Acetyl chloride and excess of acetic anhydride was distilled off at 6 mm. The residue was dissolved in CHCl₃ (10ml), cooled to 0$^{\circ}$C, and then a solution of the chiral triethanolamine (643mg, 2.5mmol) in CHCl₃ (20ml) was added dropwise within 30min. The reaction mixture was stirred at room temperature for 12h, the solvent evaporated, and the residue chromatographed on silica gel/CH₂Cl₂:ethylacetate=10:1. The corresponding product was obtained as a white solid. X-ray quality crystals were grown by slow evaporation of a solution in CH₂Cl₂/Et₂O at room temperature.

Yield 270 mg (36 %); HPLC-ESI m/e 297 (M⁺); calculated for C₁₅H₂₇NO₃Si: 297.47.

 

 

Table 3: ¹H NMR (CDCl₃) for 1( for numbering see figure 3)

$\delta$ (ppm)	mult.	J (Hz)	Int.	assignment
-0.14	s		3H	15
0.90	s		3H	9 (anti to C-7)
1.22	s		3H	8 (syn to C-7)
1.62	d	10.4	1H	7 (anti to CMe2)
1.76	m		1H	5
1.87	m		1H	6
1.88	m		1H	4
1.93	m		1H	2
1.95	m		1H	5
2.07	m		1H	6
2.15	m		1H	7 (syn to CMe2)
2.75	d	13.5	1H	10
2.78	m		3H	12 or 14
2.85	d	13.5	1H	10
2.91	m		1H	12 or 14
3.73	m		2H	11 or 13
3.74	m		2H	11 or 13

 

 

Table 4: ¹³C NMR (CDCl₃) for 1( for numbering see figure 3)

$\delta$ (ppm)	mult.	assignment
-0.85	CH3	15
23.64	CH3	9
25.09	CH2	5
27.30	CH2	7
27.40	CH3	8
34.30	CH2	6
37.54	Cq	3
40.29	CH	4
54.11	CH2	12 or 14
54.72	CH	2
54.72	CH2	12 or 14
57.70	CH2	11 or 13
57.90	CH2	11 or 13
64.55	CH2	10
76.58	Cq	1

  

Figure 3: Structure and numbering scheme for 1.