The importance of polytungstates as model compounds for homogeneous or homogeneous-heterogeneous catalysis is now well recognized, because of the triangular array of their tungsten bridging oxygens on their surfaces which resemble metal oxide surfaces. On the other hand, 183W nuclear magnetic resonance has proven to be a very good tool for determining the overall symmetry and structure of such polytungstates. Numerous efforts have been undertaken to predict a confident assignment of each tungsten line and to study the electronic changes induced on the poly tungstate anion shell in the 1-11 series by the introduction of heteroelements such as transition metals. We show that only direct proofs of the tungsten-tungsten connectivities allow an unambiguous conclusion, in contradiction with all the actually proposed methods. The direct tungsten connectivity is furnished by 2-dimensional 183W NMR on tungsten satellites (COSY and 2D INADEQUATE). The results obtained on Li7PWn039, Na7PWn039, Na8SiWn039, and Na5PPbWu039 invalidate previously published conclusions.

Thiobenzoylisocyanat (3) reagiert mit den Verbindungen der Uberschrift zu Derivaten des 1,2,4-Thiadiazols (l), Thiazols (2) und 1,2,4-Oxddiazols (4).Thioacyl Isocyanates, IX 1) Reaction with Nitrosobenzene, Diazoalkanes, and Nitrones to 5-Membered Rings Thiobenzoyl isocyanate (3) affords derivatives of 1,2,4-thiadiazole (l), thiazole (2), and 1,2,4-oxadiazole (4) by reaction with nitrosobenzene, diazoalkanes, and nitrones, respectively.

Thiobenzoyl‐isocyanat reagiert mit aromatischen Ketenen und aromatischen Keteniminen im Sinne einer 4 + 2‐Cycloaddition zu den Heterocyclen 2a–e und 3a–d der Überschrift.

Reaktionen von A1-H-und Al-C-Bindungen mit gespannten Reactions of AI-H and AI-C Bonds with Strained Olefins and I ,fi-DienesThe al -H addition to hexa-I ,5-dienes, which leads to cyclopentylmethylalanes 0 , has been extended to I ,2-dialkylsubstituted cis-4,5-divinylcyclohexenes 17 and 21, cis-I ,2-divinylcyclohexane (23) and cis-l,2-divinylcyclobutane (6). The al-H elimination from the cyclic alanes from 17 and 21 leads to the formation of the methylene derivatives 20 and 22 in high yields. The cyclic alanes derived from 6 yield 12 in only small amounts. This is attributed to strain in the double bond in 12. The effect of strain on the al-H and al-C addition and elimination reactions in rhe double bond system has been studied in the case o f bicyclo[2,2,l]hept-2-ene (26) and dicyclopentadiene (30).

cessible by treatment of methallyl chloride with sodium amide in boiling tetrahydrofuran 131. Surprisingly, however, reaction with potassium amide under otherwise identical conditions proceeds via route (a) to give a 36% yield of methylenecyclopropaiie I Z ) , as the only C4Hh hydrocarbon, instead of ( l ) .After removal of oligomers, e.g. C8H12 and C12H18, compound (2) is obtained in 97 % purity (IR [41, 1H-NMR 151, and mass spectral5J). Thus the preparation of (2) by equation (a) is superior to all previously known methods 14-61. Compound(2) is also formed quantitatively when ( I ) is passed through a suspension of KNHz in boiling THF, so that ( I ) cannot be ruled out as an intermediate in reaction (a). Compound (2) and tetraethyldiborane react together according to equation (b) at -10 to 0 "C to give diethyl(cyc1o-propylmethy1)borane (3), which rapidly isomerizes at room temperature to diethyl-3-butenylborane ( 4 ) [IR spectrum: 1637 (vc=c). 990 (-{=cH). 910 cm-1 (Y-CHJ] in a manner analogous to cyclopropylmethyllithium 171 and cyclopropylmethyimagnesium 181. However, in the presence of pyridine the cyclopropylmethyl group of ( 3 ) remains intact.