J. Org. Chem. 1992,57,40-46
40
Rigidly Hollow Hosts That Encapsulate Small MoleculesfJ92 Martin E. Tanner, Carolyn B. Knobler, and Donald J. Cram* Department of Chemistry and Biochemistry, University of California at Los Angeles, Los Angeles, California 90024 Received June 4, 1991
New chiral host systems 1and 2 possessing C3 symmetry have been designed and synthesized. Molecular models of 1 and 2 indicate they contain small enforced cavities and three portals complementary to small molecules. The crystal structure of 1.2CH3CN shows one molecule of CH3CN is encapsulated and the second exista as a solvate. A crystal structure of 2.2CH30H shows one CH30H molecule is encapsulated and a second serves as a solvate. A crystal structure of 2-CH2Cl2shows the host to be empty and that the CHzC12acta as a solvate to provide (by disorder) a C3 pattern about the C3 axis of the host. In CDC13solutions (CDC13is too large to occupy its cavity), 1 complexed 02,N2, HzO, and C 0 2 readily and reversibly ('H NMR spectra), particularly at low temperatures. In CDC13solution, 1 binds CH30Hwith K , = 10 M-', AGO295 = -1.4 kcal mol-', AH N -6.6 kcal mol-', and A S = -18 cal mol-' K-l. It also binds CH3CN,but much more weakly. Triamine 2 in CDC13binds 02,N2,and H20weakly and CH30H with a K , = 47 M-l, AGO245 = -2.3 kcal mol-', AH N -8.5 kcal mol-', and AS N -21 cal mol-' K-'. This host binds CH3CNat 295 K with a K, in the range of 1-10 M-', and CH3CHz0H with a K , 300 OC; 'H NMR (500 MHz, degassed CDC13)6 2.72 (d, 3 H, CHp, J = 15.7 Hz), 3.25 (d, 3 H, CH2, J = 12.2 Hz), 3.41 (d, 3 H, CH2,J = 12.5 Hz), 3.47 (d, 3 H, Heq, J = 13.5 Hz), 3.47 (d, 3 H, CH2,J = 16.1 Hz), 3.98 (s,9 H, OCH,), 4.05 (d, 3 H, CH2, J = 11.7 Hz), 4.07 (d, 3 H, CH2, J = 11.8 Hz), 4.57 (d, 3 H, H a , J = 13.4 Hz), 6.37 ( 8 , 3 H, ArHb), 6.69 (s, 3 H, ArHa), 7.00 (s, 3 H, AH), 7.01 (s,3 H, ArH), 7.12 (s,3 H, ArH). MS (xenon FAB, NOBA matrix) m/e 754 (M+ + 1, 100). Anal. Calcd for C51H51N303-H20: C, 79.35; H, 6.92. Found: C, 79.21; H, 7.16. ComplexationStudies. Solutions for quantitativestudies were prepared in volumetric glassware. All studies were performed on a 500-MHz spectrometer. The temperature of the probe was calibrated using the difference in chemical shifta between the two peaks of methanol (below 295 K) or ethylene glycol (above 295 K). All degassed samples were prepared by freezing the sample in liquid nitrogen, evacuating to 0.1 Torr, and thawing. This was repeated three times, and on the final cycle the NMR tube was sealed prior to thawing. Oxygen- and nitrogen-saturatedsamples were prepared by bubbling a vigorous stream of the gas through the NMR sample for a minimum of 10 min immediately before collecting the data. Additional solvent was added to the tubes prior to saturating to compensate for solvent loss due to evaporation. Crystal StructureDeterminations. Compound 1.2CH3CN crystallized from CH2C12/CH3CNas colorless parallelepipeds in the triclinic system PI. Unit cell dimensions are as follows: a = 11,710 (2) A, 6 = 11.809 (2) A, c = 28.075 (4) A, a = 96.930 (3)O, fi = 93.594 (3)O, y = 119.334 (3)O, V = 3327 A3,Z = 2. The crystal was examined on a modified Syntex PI diffractometer, CuKa radiation, at 25 "C. The structure was determined by direct methods. Refinement of 387 + 28 parameters (2 blocks, 5753 reflections with Z > 3 4 has an agreement value, R, currently at 0.122. Compound 2.CH2C12 crystallized from CH2C12/hexaneas colorless parallelepipeds in the rhombohedral system R3. Unit cell dimensions are as follows: a = 17.054 (4) A, y = 49.68 (l)', V = 2650 A3 (rhombohedral cell), a = 14.301 (3) A, c = 44.65 (1) A, V = 7950 A3 (hexagonal cell), 2 = 6(1/Bmolecule in the asymmetric unit). The crystal was examined on a Huber diffractometer, MoKa radiation, at 25 OC. The structure was de-
J. Org. Chem. 1992,57, 46-49
46
termined by direct methods. Refmement of 105parameters (1019 reflections with I > 3a(I)) has an agreement value, R , currently at 0.182. We believe this relatively high value is at least partly attributable to the high degree of disorder in these crystals. Compound 2.CH30H crystallized from CH30H/CHC13 as colorless parallelepipeds in the rhombohedral system R3. Unit cell dimensions are as follows: a = 17.090 (2) A, y = 49.33 (l)', V = 2637 A3 (rhombohedral cell), a = 14.262 (2) A, c = 44.914 molecule in the (6) A, V = 7912 A3 (hexagonal cell), 2 = 6 asymmetric unit). The crystal was examined on a Syntex Pi diffractometer, CuKa radiation, at 25 OC. The structure was determined by direct methods. Refinement of 118 parameters (1233 reflections with I > 3 4 0 ) has an agreement value, R , currently at 0.124. Complete crystallographic details are provided in the supplementary material.
Registry No. 1, 137334-67-9; l.Nz, 137334-76-0; 1.02, 137334-77-1;1.H20, 137334-78-2;lC02,137362-96-0;l.MeOH, 13733479-3;2,137334-68-0;2.Nz,137334-80-6; 2*02,137334-81-7; 2.MeCN, 137334-82-8; 2.EtOH, 137334-83-9; 3, 51760-22-6; 4, 137334-69-1; 5, 137334-70-4; 6, 137432-38-3; 7, 137334-71-5; 8, 137334-72-6; 9, 137334-73-7; 10, 137334-74-8; 11, 137334-75-9; TsNH2,70-55-3;BCl,, 10294-34-5;sodium anthracenide, 1226148-2; N-formylmorpholine, 4394-85-8. Supplementary Material Available: Figures A, B, and C as 'H NMR spectra; listings of crystallographic experimental conditions, Figures ls, 28, and 38, of the three host molecules characterized by X-ray diffraction studies, positional and thermal parameters, and interatomic distances and angles for 1.2CH3CN, 2.CH30H, and 2CHzCl2(33 pages). Ordering information is given on any current masthead page.
Ring-Opening Reactions of a-Stannyl Epoxides with Metal Hydrides and Organocuprates J. Michael Chong* and Eduardo K. Mar Guelph- Waterloo Centre for Graduate Work in Chemistry, Department of Chemistry, University of Waterloo, Waterloo, Ontario, Canada N2L 3Gl Received July 1, 1991
a-Epoxyorganostannanesare attacked by metal hydride reagents (DIBAL-H, LiAlH,, REDAL) and MezCuLi at the avbon atom proximal to the tin atom and directly at the tin atom. For example, tributyl(epoxyethy1)stannane (5) reacts with DIBAL-H to give a mixture of 2-(tributylstannyl)ethanol(7) and tributyltin hydride. Reaction of 5 with MezCuLi affords predominantly 2-(tributylstannyl)propan-l-o1(8) and some Bu3SnMe. Similarly, 3-(tributylstannyl)oxiranemethanol (lO) reacts with REDAL and MezCuLito provide products of nucleophilic attack at C-3. Cleavage occurs with inversion of stereochemistry. Tributyl(3,4-epoxybutyl)stannane(21) reacts with LiA1H4to give secondary alcohol 22 aa the sole product. While the nucleophilic opening of a-epoxyorganosilanes has been reasonably well-documented,' the literature contains no detailed reports of such reactions with the corresponding stannanes. In fact, a-epoxyorganostannanes do not seem to have been the subject of much attention.2 In connection with our work with a-alkoxyorganostannanes,3 it was of interest to study the regioselectivity of the nucleophilic ring opening of a-epoxyorganostannanes. In particular, we wished to ascertain whether ring opening of 1 would afford a-hydroxystannanes 2 (which could be converted into synthetically useful a-alkoxyorganostannanes) or 0-hydroxystannanes 3 (eq l). Our findings in this area are reported below. OH
Bu3Sn&I 1
?-!,_!
kR .
Bu3Sn
Or
(I)
Bu,Sn*R
2
3
Scheme I Bu3Sn/\\ 4
mCPBA
-
Bu,Sn
A0 5
Scheme I1 B u , S n v O H g
TBHP
k;
Bu3Sn&OH REDAY lo
OH
Results and Discussion The epoxide derived from tributylvinylstannane (4) has been prepared previously in low yield (12%)by treatment of 4 with m-CPBA in benzene: A simple change in sol(1) (a) Colvin, E. W. Silicon Reagents in Organic Synthesis; Academic Press: New York, 1988; Chapter 4. (b) Eisch, J. J.; Trainor, J. T. J. Org. Chem. 1963,28,487. (c) Eisch, J. J.; Trainor, J. T. J. Org. Chem. 1963, 28,2870. (d) Hudrlik, P. F.; Peterson, D.; Rona, R. J. J.Org. Chem. 19'15, 40,2263. (e) Schaumann, E.; Kirsching, A. J. Chem. SOC.,Perkin Trans. I 1990, 419. (f) Jankowski, P.; Marczak, S.; Masnyk, M.; Wicha, J. J. Chem. SOC.,Chem. Common. 1991, 297. (2) (a) Kitano, Y.; Matsumoto, T.; Okamoto, S.; Shimazaki, T.; KObayashi, Y.; Sato, F. Chem. Lett. 1987,1523. (b) Eisch, J. J.; Galle, J. E. J. Organomet. Chem. 1988,341,293. (c) Lohse,P.; Loner, H.;Acklin, P.; Sternfeld, F.; Pfaltz, A. Tetrahedron Lett. 1991, 32, 615. (3) Chan, P. C.-M.; Chong, J. M. Tetrahedron Lett. 1990,31,1985 and references cited therein.
B u , S n Y O H OH 11
Bu3SnLOH
6H 12
vent dramatically improved the yield of 5: When vinylstannane 4 was allowed to react with m-CPBA in CHCl,, epoxide 5 was isolated in reasonable yield (67%) after column chromatography. There appear to be no reports of studies on nucleophilic openings of 5.5 When 5 was treated with DIBAL-H at low (4) Ayrey, G.; Parsonage, J. R.; Poller, R. C. J. Organomet. Chem. 1973, 56, 193. (5) Reaction of 4 with a magnesio cuprate was reported in footnote 11 oE Matsubara, S.; Mitani, M.; Utimoto, K. Tetrahedron Lett. 1987,28, 5857.
0022-3263/92/1957-0046$03.00/00 1992 American Chemical Society
