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The ketene tBu2C=C=O is prepared from tBu2C=O in three steps (performable as a two‐stage operation) through elimination of HCl from the intermediate product tBu2CCl–CH=O. The acid tBu2CH–CO2H, obtainable in two, three, or four preparative stages from tBu2C=O, adds slowly to the ketene to produce the anhydride (tBu2CH–CO)2O. Elemental lithium together with ClSiMe3 converts tBu2CCl–CH=O into tBu2C=CH–OSiMe3, which is a durable precursor of tBu2CH–CH=O, making this aldehyde easily and cheaply available from tBu2C=O. By exclusion of alternative mechanistic possibilities, the reduction of tBu2CCl–CH=O by tBuMgCl is shown to involve at least one single‐electron transfer, leading to the enolate tBu2C=CH–OMgCl, which can be converted into tBu2CH–CH=O (three steps from tBu2C=O) or into tBu2C=CH–OSiMe3. Hydride transfer from NaBH4 to tBu2CCl–CH=O affords tBu2CCl–CH2OH, the transformations of which provide an entertaining set of SN1‐type reactions. Several other examples of carbenium‐type behavior are encountered in this gem‐tBu2 system; they are attributed to steric congestion, which also impedes bond rotations in the anhydride and in two esters. A convenient route to tBu2CH–C≡N (five steps from tBu2C=O) uses the conversion of tBu2C=CH–OSiMe3 into tBu2CH–CH=NOH. The slow thermal (Z)/(E) equilibration of tBu2CH–NH–CH=O reveals the ranking of ecliptic repulsions as H3C < tBu < tBu2CH.

2,2,4,4-Tetramethyl-3-pentanimine (3)is efficiently prepared by a Barbier-type reaction of pivalonitrile (1) with an excess of tert-butyl chloride (2) and metallic lithium in ether. Its pu-rification by extraction into aqueous acid and slow hydrolysis permit an inexpensive and very simple production of di-tertbutyl ketone (4).Numerous possible applications of 2,2,4,4-tetramethyl-3-pentanone (4) as a source of gem-di-tert-butyl compounds call for a ready access to this ketone. But despite a variety of published preparations, the commercial substance 4 is sold at an exorbitantly high price (currently at least DM 2400 per mol), perhaps indicative of severe problems in production or purification. We are now able to remedy this situation by communicating the following simple and efficient route to di-tert-butyl ketone (4).

Komplexverbindungen des Typs , mit M = Fe, Co und Thiodibenzoylmethanat (TDBM) und N‐(Morpholinothiocarbamoyl)‐benzamidat (MTBA), wurden synthetisiert. Mittels Molmassebestimmung, IR‐ und ESCA‐Spektroskopie sowie magnetochemischen Untersuchungen wurde nachgewiesen, daß der Eisenkomplex 1 als schwefelverbrückter Zweikern‐komplex [Fe(TDBM)2NO]2 vorliegt, in dem jedes Eisenatom sechsfach koordiniert ist. Die Kobalt‐komplexe Co(TDBM)2NO, 2, und Co(MTBA)2NO, 3, liegen monomer in quadratisch‐pyramidaler Struktur vor. In allen Fällen weisen die ESCA‐Spektren formal dreiwertige Zentralmetalle mit negativ geladenem Nitrosylliganden aus.

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