Ketones adamantyl—

Bromomethyl-l-adamantyl ketones were condensed with thioamides of carboxylic or carbonic acids to give the corresponding thiazoles (613). 

Vinyl cations also have been invoked as intermediates in the addition of carbonium ions generated in strong acid to acetylene (50-53). Sasaki et al (50) observed 1-adamantyl methyl ketone, 25, as the sole product in the reaction of acetylene with 1-bromoadamantane in concentrated H2SO4 at 5°. Bott (51), on the other hand, reported a mixture consisting of 75% 1-adamantylacetaldehyde,... 

Protoadamantanone has been prepared by the nitrous acid deamination of 2-amino-l-adamantanol (77%), by aprotic diazo-tization of endo-7-aminomethylbicyclo[3.3.1]nonan-3-one in benzene with an equivalent amount of acetic acid (67%), and by thermolysis of 1-adamantyl hypohalites followed by base-promoted cyclization of the resulting halo ketones (32-37%)." In spite of low and erratic yields, the last reaction sequence has provided the most convenient route to the protoadamantanes, since the other two approaches require lengthy syntheses of the starting materials. 

The procedure described here is a modification of one involving the thermal fragmentation of 1-adamantyl hypoiodite and cycliza-tion of the resulting iodo ketone/ By means of this procedure, 4-protoadamantanone is obtained from 1-adamantanol with consistent yields in the range of 71 to 82% and a purity greater than 98%. This method is also applicable to the preparation of other polycyclic ketones from the related bridgehead alcohols with a-bridges of zero, one, or two carbon atoms (see Table I). 

Highly Reactive Calcium for the Preparation of Organocalcium Reagents Preparation of 1-Adamantyl Calcium Halides and Their Addition to Ketones. 

Steric effects on both the amide and the acyloxyl side chain are similar. Tert-butyl and adamantyl groups on the amide side chain in 29v, 29x, 29c, and 29e (Table 2 entries 53 and 54, 63 and 65) result in lower stretch frequencies that, on average, are only 40 cm-1 higher than their precurser hydroxamic esters. Streck and coworkers have suggested that such changes in dialkyl ketones can be ascribed to destabilisation of resonance form II through steric hindrance to solvation which, in the case of tert-butyl counteracts the inductive stabilisation.127... 

R. D. Rieke, T.-C. Wu, and L. 1. Rieke 147 HIGHLY REACTIVE CALCIUM FOR THE PREPARATION OF ORGANO-CALCIUM REAGENTS PREPARATION OF 1-ADAMANTYL CALCIUM HALIDES AND THEIR ADDITION TO KETONES 1 -(1 -ADAMANTYLJCYCLOHEXANOL... 

For example, acetyladamantane and isopropyl methyl ketone gave 1-adamantyl-acetamide in 85% yield and N-acetyl-isopropylamine in 46% yield, respectively [79]. A similar a-cleavage was observed in the electrochemical oxidation of the a-branched cyclic ketone (43) using Et3N-5HF as an electrolyte (Scheme 16) [81]. 

Cahonic iridium complexes bearing imidazol-2-ylidene hgands were applied as TH catalysts by Hillier et al. [48]. Here, [lr(cod)(py)(L)]Pp6 (L= IMes, l,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene (53a), IPr, l,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene (53b) and ICy, l,3-bis(cyclohexyl)imidazol-2-ylidene (53c) were employed as catalysts for TH from 2-propanol to various unsaturated substrates, and compared to [lr(cod)(py)(PCy3)]PF6 and complexes formed in situ from [Ir(cod)(py)2]PF,5 and diazabutadienes (RN=CHCH=NR, DAB-R R = cyclohexyl, DAB-Cy 2,4,6-trimethylphenyl, DAB-Mes adamantyl, DAB-Ad 2,4,6-trimethoxyphenyl, DAB-trimethoxyphenyl). AH complexes were achve catalysts for the TH of acyclic ketones, with complex 53c being the most achve, showing 100% conversion of BuC(0)Me and PhC(0)Ph in 25 and lOmin, respechvely, using 0.025 mol% of catalyst and KOH in PrOH at reflux (Scheme 4.20). 

Treatment of hydrazones derived from 1-adamantyl phenyl ketone, pivalophe-none and benzophenone with sulfur monochloride gave pentathianes 232 and hexathianes 233 along with the corresponding ketones and thioketones as the main products (1997H255 Scheme 124). 

Bredt s rule. In this way, 1-adamantyl p-methoxyacetophenone 86a was forced to yield only cyclobutanols 87a and 88a as photoproducts [281]. Whereas (benzene) solution phase irradiations of 86a yielded a 2.6 ratio of 87a/88a, the solid state photoproduct ratio, 0.5, favors the more sterically hindered cyclobutanol. X-Ray diffraction studies predict a chair-like y-hydrogen abstraction pathway for 86a (in contrast to the boat-like transition states of 82) in which the C=0-Ha distance is 2.67 A. Other abstractable hydrogens (Hb) are at least 0.3 A farther from the carbonyl oxygen (Scheme 44). If i-BR has a conformation which mimics that of the ketone, its least motion pathway favors formation of the more sterically hindered cyclobutanol 88a. 

Oxasiletene, the unsaturated analogue of oxasiletane, was first postulated by Seyferth and coworkers as a reactive intermediate in the reaction of l,l-dimethyl-2,3-bis(trimethylsilyl)-l-silirene with dimethyl sulfoxide25. The photochemical generation of siladienone intermediate 28 from (pentamethyldisilanyl)diazomethyl 1-adamantyl ketone... 

In this section we are considering cyclic ketones in which the >CO group is not part of the ring. The two compounds of greatest interest here are 1-adamantyl methyl ketone120 (51a) and bis(l-adamantyl)ketone121 (51b) with their respective gas-phase enthalpies of formation of —298.3 3.2 and —367.8 5.0 kJmol-1. Abboud and coworkers121 considered formal reaction 42... 

The treatment of hydrazones derived from l-adamantyl(phenyl)ketone, pivalophenone, and benzophenone with S2C12 gave hexathiepanes 131 (Figure 31) along with other products as tetra- and pentathianes (1997H255). 

Treatment of 1-bromoadamantane with AlBr3 in the presence of ethylene at -75 °C to give l-(j3-bromoethyl)-adamantane 202) followed by reduction 20°) results in good yields of 1-ethyladamantane (Eq. (63)). Wolf-Kishner 164) or Clemensen 203) reduction of commercially available methyl adamantyl ketone provides an alternative route for the preparation of this compound. 

Scheffer et al. provided another unimolecular asymmetric transformation involving the Norrish type II reaction, a well-known excited state process of ketones that is initiated by an intramolecular hydrogen atom transfer from carbon to oxygen through a six-membered transition state (Scheme 5). [19a] An adamantyl ketone derivative 27 was found to crystallize from ethanol in very large prisms in the chiral space group P2 2 2. Upon irradiation of these crystals to approximately 10% conversion, the chiral cyclobutanol derivatives 28 were afforded as the major products in 80% ee. 

Why does the adamantyl compound shown below behave more like a ketone than an amide Hint Draw the corresponding resonance hybrid.)... 

The reaction of Brook s ketone with an excess of Et3GeLi followed by hydrolysis gave a 1 2 mixture of a trisilacyclobutane and (adamantoyl) adamantyl carbinol. It was suggested that this reaction involves the formation of a transient disilene. The structure of the trisilacyclobutane was established by X-ray analysis (equation 197)205. 

The achiral adamantyl ketone in Sch. 29 crystallizes in the chiral space group P212121 [164]. Upon irradiation of single crystals of this ketone, a cyclobutanol is obtained via the Norrish-Yang reaction, while in solution one obtains a mixture of four cyclobutanol isomers. In the solid state a single cyclobutanol is obtained with e.e. >80%. 

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