3.3- dimethyl-l-butyne

Hexyne, 2-hexyne, 3-hexyne, 3-methyl-Hpentyne, 4-methyl-l-pentynep 4-methyl-2-pentyne, 3.3-dimethyl-l-butyne... 

Complex condensation products are obtained by reaction of the alkyne complex with excess of 3,3-dimethyl-l-butyne, which yields two isomeric products of formulas Ru3(CO)6[HC2C(Me)3-COCH2CMe3][HC2CMe3]2 (125). The X-ray structure of one of those adducts (Fig. 19) shows that both dimerization of two alkyne molecules and the insertion of carbon monoxide into the alkyne metal bonds have occurred. The Ru-Ru distances of 2.820,2.828, and 2.686 A in the ring are of interest. The value of 2.686 A is one of the shortest found in a... 

Dimethyl-l-butyne, 2408 1,8-Diphenyloctatetrayne, 3788 Hepta-l,3,5-triyne, 2641 l-Heptene-4,6-diyne, 2707... 

The reaction of excess 3,3-dimethyl-l-butyne with Co2(CO)8 yields violet crystals of (C2HR)3Co2(CO)4 [R = 0(0113)3], which upon reaction with a OOI4 solution of bromine at 0°0 produce l,2,4-tri-ier<-butylben-zene, the first benzene derivative with ortho ieri-butyl substituents (368). This latter reaction, coupled with the infrared spectral and magnetic moment data, indicates structure (161) for the complex. 

Bayer and Siebert reported the reaction of 3,3-dimethyl-l-butyne with -BuLi in pentane, followed by the addition of boron trichloride to afford the intermediate dichloro(3,3-dimethylbut-l-ynyl)borane that was hydroborated with dichloroborane formed in situ to give l,l-bis(dichloroboryl)-3,3-dimethylbutene 51 (Scheme 6) <2002ZN1125>. When the latter was subjected to halogen exchange with boron triiodide, it was converted into the corresponding tetraiodide 52, which underwent a redox reaction with hex-3-yne to give the 2-(2,2-dimethylpropylidene)-l,3-diborole 22 in 73% yield. 

Under similar conditions phenylacetvlene. 1-hexyne. 3.3-dimethyl-l-butyne. and trimethylsi-lylacetylene give f )-l-phenyl-1-pen ten-3-one, ( )-4-nonen-3-one, (Fj-6.6-dimethyl-4-hepten-3-one, and ( )-l-trimethylsilyl-l-penten-3-one in 76, 68, 93, and 62% yields, respectively5. Thus, the reaction of terminal acetylenes proceeds with high stereo- and regioselectivity. The propionyl group is introduced at the less sterically hindered acetylenic carbon atom. These reactions arc assumed to include /i-acylvinylrhodinm complexes as the common key intermediates. 

Methylphenylacetylene (1-phenylpropyne), fert-butylphenylacetylene (1-phenyl-3,3-dimethyl-l-butyne), biphenylene, and diphenylacetylene (diphenyl-ethyne) were prepared by reliable methods. The other hydrocarbons were purchased and then purified until they met published criteria of purity (i.e., mp, thin layer chromatography, IR, and UV). The same procedure was followed for phenoxathiin, phenothiazine, and thianthrene. Finally, silicon derivatives of alkynes, alkenes, alkadienes, and arenes were made according to published procedures. 

For instance, attempts at isolating donor-free alkynylboranes have been hampered by spontaneous polymerization. The first donor-free tris(alkynyl)borane, tris(3,3-dimethyl-l-butynyl)borane (30), has only recently been obtained by reaction of deprotonated 3,3-dimethyl-l-butyne with boron trichloride at —78°C in pentane (equation 32). The alkynylborane (30) was fully characterized by multinuclear NMR spectroscopy, mass spectrometry, and X-ray crystallography. The NMR signal of (30) shows a remarkable shift of 5 = 48, which is upfield from typical shifts of alkyl-and alkenylboranes. The crystal structure of (30) shows similar C-C bond lengths, but significantly shorter B-C bonds in comparison to those observed for the donor-stabilized complexes (30) D indicative of a small degree of p - p interactions between the sp -boron atom and the sp-hybridized carbon. Weak r-overlap was further confirmed by ab initio calculations. It is this r-interaction that has been exploited for the development of nonlinear optical (NLO) materials based on alkynylboranes as described in Section 7.1. ... 

Each of the dibromides shown yields 3,3-dimethyl-l-butyne when subjected to double dehydro-halogenation with strong base. 

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