From Allenes to Tetracenes: A Synthetic and Structural Study of Silyl‐ and Halo‐Allenes and Their Dimers

A Synthetic and X‐ray Crystallographic Study of Zinc and Platinum Complexes of 4,5‐Diazafluoren‐9‐one (Dafone) and Dicobalt Hexacarbonyl Derivatives of 9‐Phenylethynyl‐4,5‐Diazafluoren‐9‐ol: Chelation versus Monocoordination

“…Conversion to the required 3,3-(biphenyl-2,2Ј-diyl)-1-arylallene 3 can be accomplished either by reaction with BF 3 /Et 3 SiH (to form an alkyne 2, which readily rearranges under basic conditions) [4][5][6] or by formation of the bromoallene 4, [7] followed by lithiation and hydrolysis. [8] Subsequent thermolysis of the allenes yields tetracenes 5. This general procedure has since been extended to include allene dimers containing halogens, and also silyl, [8,9] phosphane [10] and ferrocenyl [11] substituents.…”

Solvent‐Mediated Generation of Cobalt‐Cluster‐Stabilised Propargyl Cations and Radicals: Allyl Migration versus Peroxide Formation

“…This same centrosymmetric disorder phenomenon is also found in the corresponding bis(trimethylsilyl)propargylallene. [32] Interestingly, a Cope rearrangement of the hexa-1,2-diene-5-yne 26 would regenerate itself, presumably through a twofold symmetric transition state.…”

“…Syntheses of 4, 17, 18, 19, 20 and 21: 9-(Trimethylsilyl)ethynyl-9H-fluoren-9-ol [32] (2.45 g, 8.8 mmol) was treated with two equivalents of nBuLi (11.0 mL of a 1.6 m hexanes solution, 17.6 mmol) at À78 8C and left to react for 4 h at low temperature. A solution of allyldimethylchlorosilane (1.1 mL, 8.8 mmol) in anhydrous diethyl ether (20 mL) was then added dropwise and the solution allowed to warm gradually to room temperature.…”

Reactivity of 3-halopropynols: X-ray crystallographic analysis of 1,1-dihalocumulenes and 2+2 cycloaddition products

“…Unfortunately, our attempts to increase the yield of 10 by addition of iodine source (I2, NaI, NIS, tetrabutylammonium iodide (TBAI)) failed and we decided to switch to 'wet' conditions. We used literature procedure 21 and the reaction of 4 with HI(aq) gave 10 in 62% yield. The reaction of 5 with BF3·Et2O gave a complex mixture of products.…”

“…19 Their subsequent transformations provide complex molecules with broad carbon core diversification. [20][21][22] Herein, we report on the preparation and characterization of two 1,1-dihaloallenes and some products of their cycloaddition. Because of the complicated molecular structure of these compounds, we focused on X-ray crystallographic methods for structure determination.…”