Hooz reaction

A study on stereodefined boryl enolates that employed both pure (Z)- and ( )-dialkylboryl enolates has been carried out by Masamune et al Hooz reaction involving a-diazocarbonyi compounds (Scheme 3) and a trialkylborane provides exclusively (0)-alkenyloxyboranes, which can be isomerized cleanly to the corresponding Z(0)-isomers.- The Z((9)-dibutylboryl enolates (17) react with various aldehydes exhibiting uniformly high syn selectivities (syn.anti > 95 5), while the corresponding (0)-isomers (18) are converted into the anti aldol products with somewhat lower selectivities (Scheme 15). 

Hooz reaction of boranes with diazo compds. 24,817 Huang Minion rednctimi s. Wolff-Kishner Hiinig base s. Ethyl-diisopropylamine Hydantoin ring,... 

Revell, J. D. Ganesan, A. Synthesis of functionalized 1,5-cyclooctadienes by LICKOR metalation. J. Org. Chem. 2002, 67, 6250-6252. Hooz, J. Calzada, J. G. McMaster, D. An efficient coupling reaction of anionic propargyl and organic halides. Tetrahedron Lett. 1985, 26, 271-274. 

Hooz, J. and Bridson, J. N. A method for the regiospecific synthesis of Mannich bases. Reaction of enolborinates with dimethyl (methylene) ammonium iodide, J. Am. ChertL Soc.. 95, 602, 1973. 

Kegiospecific synthesis of Manmch bases. Hooz and Bridson have described a new rcgiospecific synthesis of certain Mannich bases which involves first reaction of a trialkylborane with an a-diazoketone in THF to form an cnol borinate (1) after evolution of nitrogen ceases, dimcthyl(methylene)ammonium iodide (2) in DMSO is added. The Mannich base (3) is obtained in 85 100% yield after hydrolytic workup. Cosolvent DMSO is crucial for high yields. 

Carbon tetrachloride serves as both solvent and halogen source it is usually desirable to employ a modest excess of triphenylphosphine. Hooz has suggested that the reaction proceeds through an Sr<2 process. 

The reagent has been used successfully for conversion of hydroxy carboxylic acid esters into the corresponding chloro esters.4 Bromo esters are obtained if CBr4 is used. The replacement occurs with inversion. The method is applicable to hindered a-hydroxy esters. Hooz and Gilani5 state that the reaction is more rapid if tri-n-octylphosphine is used in place of triphenylphosphine. 

In the 1930 s and later, but before instrumental analytical methods (IR, NMR, X-ray, etc.) were easily available, the Arndt-Eistert reaction was very welcome for the characterization of degradation intermediates of natural products (Bachmann and Stuve, 1942). Bridson and Hooz (1988), and Scott and Sumpter (1993) described processes for the first step, and Lee and Newman (1988) for the overall reaction sequence in Organic Syntheses, The reported yields for both steps are excellent (84-90% each). Larock reviewed various procedures for Arndt-Eistert reactions (including the little investigated metal catalysis) in his book Comprehensive Organic Transformations (1989, p. 933). 

Lithium enolates were also generated by rhodium-catalyzed double-bond shifts in allyl lithium alkoxides [177], the cleavage of cyclopropyl ketones with lithium in ammonia [137b, 178] and various other methods [2c,d,e]. The first preparation of boron enolates, achieved by Hooz and coworkers [179], is based on a reaction of a-diazo ketones 188 with tributylborane. The primary adduct 189 releases nitrogen, andthetautomerism ofthe intermediate 190 finally leads to the boron enolate 191 (Scheme 2.55). 

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