Trimethylsilyl-substituted cyclopropenes

A C(ip )-H amination of trimethylsilyl-substituted cyclopropenes proceeds via a tandem regioselective ene reaction between cyclopropenes and azodicarboxylate to generate a hydrazodicarboxylate intermediate followed its site-selective allylic transposition (Scheme 85). ... 

Whereas the repeated lithiation-trimethylsilylation sequence of trimethyl-silylbicyclopropylidene 43 a yielded predominantly the cyclopropene derivative 51 [54], bicyclopropylidenecarboxylates 42-Me, 42-fBu after repeated deprotonation and carboxylation retain the bicyclopropylidene moiety and give 2,2-disubstituted products 52-R only (Scheme 9) [55]. So far, alkylbicyclopropyl-idenes 43 e, f, g have not been induced to undergo deprotonation and a second substitution [56a]. The urethane 53 with a nitrogen directly attached to the skeleton, more easily than any other bicyclopropylidene derivative, rearranges to... 

At 60 °C, bicyclic titanacyclopentene complex 179 rearranges to 2-vinyl-substituted titanacyclobutene complex 180 in indeterminate yield (Equation 91) <1993CB1541>. This transformation proceeds by bis(trimethylsilyl)ethyne extrusion, rearrangement of the residual coordinated cyclopropene to vinylalkylidene, and [2+2] cycloaddition to reincorporate alkyne. 

Cyclopropenes undergo an oxidative cleavage to yidd substituted enones, as shown in equation (27). The reaction is believed to proceed through the unstable qwxide. The regioselectivity is genoaOy low if R 9 R, but if one of the substituents is trimethylsilyl a hi y selective conversion to the a-silyl enone takes place. There is one report of a similar oxidative cleavage that takes place with thallium(ni). ... 

Several reports have appeared on the preparation and chemistry of 1,2,3-triazines. Heating trimethylsilyl azide with perchloro- or perbromo-cyclopropene gives the corresponding triazine (291 X = Cl or Br). Nucleophilic substitution of these trihalogeno-compounds occurs first at the 4- and 6-positions and only finally at the 5-position depending upon the conditions and the nucleophile, mono-, di-, or tri-substitution products may be obtained (Scheme 114). ... 

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