Organoboranes in the synthesis and utility of organozinc compounds and six-membered aromatic heterocycles containing boron.

Z-1-Iodo-1-hexen-1-ylpinacolboronate and two related compounds could be prepared by hydroboration of 1-iodo-1-alkynes. These pinacol $\alpha$-iodoalkenylboronates were converted to 1,1-organobimetallics of boron and zinc, and then treated with CuCN$\cdot$2LiCl to give 1,1-organobimetallics of boron and copper. These cuprates reacted well with electrophiles such as allylic halides, 1-iodo-1-alkynes, and $\alpha,\beta$-unsaturated ketones and esters, affording polyfunctional boronic esters. Oxidation of these adducts with alkaline hydrogen peroxide afforded polyfunctional ketones in good yield. 2-(1-Decyl)-1,3,2-dithiaborolane and three related compounds could be converted directly to the corresponding symmetrical dialkylzinc compounds upon boron-zinc exchange with diethylzinc. The functionalized dialkylzinc compounds thus obtained are not readily available by standard methods. These dialkylzinc compounds could be used in conjunction with CuCN$\cdot$2LiCl to form new carbon-carbon bonds upon treatment with the electrophiles mentioned above. The resulting adducts are formed in moderate to good yield. 1-Chloroboracyclohexa-3,5-diene could be treated with 3-(dimethylamino)propylmagnesium chloride followed by tert-butyllithium to afford lithium 1-(3-dimethylamino)propylboratabenzene. This lithium boratabenzene could be converted to $(\eta \sp 5$-1-(3-dimethylamino)propylboratabenzene)tricarbonylmanganese (I). The crystal structure of this manganese complex shows that it exists in the intramolecularly B-N-coordinated form with a B-N bond distance of 1.716(5) A. In toluene-d$\sb8$ solution however, the intramolecularly coordinated complex is in mobile equilibrium with its ring-opened isomer. Using $\sp{11}$B NMR spectroscopy, the equilibrium constants for this solution equilibrium have been measured over the temperature range $-$35 to 48$\sp\circ$C, allowing evaluation of $\rm\Delta H\sp\circ$ (6.0 kcal/mol) and $\rm\Delta S\sp\circ$ (23 cal/mol K). The base-catalyzed hydrostannation of diethynyl sulfide with dibutylstannane affords 4,4-dibutyl-1,4-thiastannin, which reacts with appropriate boron halides to give 4-methyl-1,4-thiaborin, 4-phenyl-1,4-thiaborin, and 4-chloro-1,4-thiaborin. Hartree-Fock-level ab initio calculations indicate a planar structure for 4-methyl-1,4-thiaborin, which is consistent with aromaticity. Low field $\sp1$H NMR signals for the thiaborins, as well as a red-shifted $\pi\to\pi\sp{\*}$ band in the ultraviolet spectrum of the methylthiaborin, also argue for some degree of aromatic character in these species. 4-Methyl-1,4-thiaborin was also converted to tricarbonyl($\eta\sp6$-4-methyl-1,4-thiaborin)molybdenum (0), which was characterized by single-crystal X-ray diffraction. Crystal data for this molybdenum complex show a striking similarity to the crystal data for borepinmolybdenum and thiophenechromium complexes, which indicates that thiaborin behaves as an arene ligand.Ph.D.Inorganic chemistryOrganic chemistryPure SciencesUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/130390/2/9722117.pd