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Distannylated bicyclo[3.2.1]octa-2,6-diene (1) with (CH 3 ) 3  Sn groups in positions exo-4 and 7 (7a), endo-4 and 7 (7b), exo-4 and 6 (7c), and probably exo-4 and endo-4 (7d) are obtained when 1 is treated first with an excess of n-BuLi/t-BuOK in alkane and then with (CH 3 ) 3  SnCl. Byproducts are monostannylated derivatives of 1 and l,4-bis(trimethylstannyl)but-2-ene (3). The formation of 7a/b/c is best understood when the two possible bicyclo[3.2.1]octa-2,6-dienyl dianions are generated as intermediates. 3,exo-4-Bis(trimethylstannyl)bicyclo[3.2.1]octa-2,6-diene (7e) is ob-tained from the corresponding dibromo derivative of 1 and (CH 3 ) 3 SnLi with 3-bromo-exo-4-trimethylstannylbicyclo[3.2.1]octa-2,6-diene (9) as an intermediate. The bicyclic stannyl com-pounds are susceptible to a 1,5-homopentadienyl shift of a (CH 3 ) 3 Sn group at relatively low temperature when the starting compound has the stannyl group in position 4 of 1 and when positions 6 or 7 are unsubstituted. Tricyclo[3.2.1.0 2.7 ]oct-3-enes with (CH 3 ) 3 Sn groups in positions exo-6 (5a), endo-6 (5b), 3 and exo-6 (10a), and 3 and endo-6 (10b) are thus obtained. On further heating, 10b gives l-trimethylstannyl-3-vinylbenzene (11). All compounds have been studied systematically by NMR spectroscopy including δ( 119 Sn), δ( 13 C), δ( 1 H),  4/5 J( 119/117 Sn- 119 Sn),  n J( 119/117 Sn- 13 C) ,  n J( 119/117 Sn- 1 H),  1 J( 13 C- 1 H ) , and  n J( 1 H- 1 H ). Among all nuclei,  119 Sn gives the most simple spectra. From the  13 C NMR spectra a series of useful increments of (CH 3 ) 3 Sn groups emerges. The most interesting coupling constants are  5 J( 119/117 Sn- 119 Sn), for which a considerable change with the dihedral angle is established, and  n J( 119/117 Sn- 13 C). For n = 3 and 4 the latter are especially useful because their angular dependence leads to unambiguous signal assignments.

zeitschrift für naturforschung b

Selektive Metallierung von BicycIo[3.2.1]octa-2,6-dien, II Distannylierte Derivate und stannylierte tricyclische Sekundärprodukte / Selective Metalation of Bicyclo[3.2.1]octa-2,6-diene, II Distannylated Derivatives and Stannylated Tricyclic Secondary Products