CYCLOHEXANONE, 2 DIAZO

Cyclohexanol, with triphenyl phosphite and mettyl iodide, 51,45 CYCLOHEXANONE, 2-DIAZO-, 51, 6... 

With cyclic a-diazo ketones, e.g. a-diazo cyclohexanone 9, the rearrangement results in a ring contraction by one carbon " ... 

Irradiation of 36a in 1,4-dichlorobenzone at 60 °C, a temperature at which thermal decomposition of the diazo compound is still negligible 24), in the presence of benzo-phenone, acetone, or cyclohexanone leads to l,3,4X5-dioxaphosphorins 56a-c (= 57a-c)33 ... 

Diazirines are the cyclic isomers of the alphatic diazo compounds. Both the diaziridines and the diazirines are starting materials for the synthesis of alkyl hydrazines. 3,3-Pentamethyl-enediaziridine can be hydrolyzed quantitatively to hydrazine. Methylamine may be substituted for ammonia in the procedure resulting in l-methyl-3,3-pentamethylenediaziridine (m.p. 35-36°, yield 62% of theoretical) and then methyl hydrazine. Use of ethylenediamine leads to ethylene bis-hydrazine via a bifunctional diaziridine (m.p. 143-144°, yield 48% of theoretical). Ammonia can also be replaced by w-propylamine or cydo-hexylamine cyclohexanone by acetone. 

In addition to previously described syntheses4-5 by diazo group transfer with deformylation,6 2-diazocyclohexanone has been prepared by two variants of this method. In one, the reaction of 2-(hydroxymethylene)cyclohexanone with -toluene-sulfonyl azide is carried out in ether/diethylamine, and an enamine is assumed to be formed as an intermediate 7 in the other, the sodium salt of the hydroxymethylene compound was treated with the lithium salt of p-carboxybenzenesulfonyl azide... 

Intramolecular carbene insertion (e.g. 1 —> 3) has long been a useful method for ring construction. Masahisa Nakada of Waseda University in Tokyo now reports (J. Am. Chem. Soc. 125 2860, 2003) that with the addition of the ligand 2 this process can be made highly enantioselective. As the starting diazo ketone 1 is easily prepared by diazo transfer to the sulfonyl ketone, this should allow facile entry to enantioenriched cyclopentanones and cyclohexanones. 

Another class of substances of interest as bifunctional diazo components consists of special diamines that can be manufactured by the reaction of aromatic amines with benzaldehyde or cyclohexanone, e.g.,16 and 16a. 

The problem with reactions like this is that both the starting material and product are ketones, so they work cleanly only if the starting material is more reactive than the product. Cyclohexanone is more reactive as an electrophile than either cyclopentanone or cycloheptanone, so it ring expands cleanly to cycloheptanone. But expansion of cyclopentanone to cyclohexanone is messy and gives a mixture of products. We shall come back to diazo compounds in more detail in Chapter 40 diazonium salts will reappear in Chapter 38 where their decomposition will provide the driving force for fragmentation reactions. 

The diazo group transfer reaction fails in nonactivated ketones because of insufficient proton labiality in the compound. This can be circumvented by introducing a formyl group via Claisen reaction to provide additional activation and this formyl group is eliminated in the course of the diazo transfer reaction.4,5 The formylation followed by subsequent diazo transfer reaction is demonstrated with cyclopentanone (52 — 53 — 54)4M, 4c a,p-unsaturated ketone (55 —> 56 — 57)4d and 4-/-Bu-cyclohexanone (58 — 59 - 60).5,21... 

Similarly, 2-formyl cyclohexanone (79), 4-formyl seven membered heterocyclic ketones (81), and 5-formylbenzfuranone (83) are converted to the corresponding diazo ketones 80, 82, and 84 usingp-tolylsulfonyl azide and p-benzoic acid sulfonylazide.43,30... 

On irradiation, 2,6-bis(diazo)cyclohexanone (104) also undergoes elimination of nitrogen accompanied by ring contraction.84 A cyclopropenone (105) rather... 

Polymer-bound arylsulfonyl azides have been tested as diazo transfer reagents (Roush et al., 1974 Diirr et al., 1981). Yields with diethyl malonate and acetylace-tone are slightly lower than those with 4-toluenesulfonyl azide. In contrast to these compounds with two neighboring activating groups, yields with monoactivated methylenes (ethyl propionate and cyclohexanone) are much lower. This method is therefore, not recommended in the described form. 

---