Saturated Cyclic Carbonyl Compounds

Intramolecular Hydrogen abstraction The terminal alkyl radicals undergo intramolecular Hydrogen abstraction to produce a ketone. 

Intramolecular Hydrogen abstraction by the carbonyl carbon atom, to 

Photo-decarboxylation Acyclic carbonyl diradical on decarboxylation give carbon monoxide, an alkene or a cyclic alkane or both. 

In the vapour-phase photolysis of cyclohexanone, the 1, 6- triplet diradical is formed by Norrish type I cleavage. 

The vapour phase photolysis of epimeric 2, 6- dimethyl cyclohexanone gives stereospecific reaction. In each case, product formation is faster than photochemical interconversion of the epimers and each epimer gives the stereospecific mixture of products. 

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The isomerisation have already been reported. The formed diradical recombines, which gives rise to thermodynamically more stable isomer. The photochemical epimerisation of 17-ketosteroids and other mentioned saturated cyclic carbonyl compounds is through Norrish type I, a-cleavage. 

Catalytic benzylation of 10 was performed under solid-liquid phase-transfer conditions to yield benzylidenemalononitrile Alkylidenemalononitriles can undergo reduction to yield the corresponding saturated malononitriles ". Aryl malononitriles 125 have been obtained from 10 and halobenzenes " or from aroyl chlorides in three steps. Surprisingly, the aliphatic malononitrile derivative 126 has been obtained when 2-indolone was reacted with 43. The same reaction was also observed for two other cyclic carbonyl compounds... 

The reaction of carbonyl compounds with glycerin-a-monochlorohydrin, CHjOHCHOHCHjCl, leads to cyclic halo acetals. Treatment of a,/3-olefinic aldehydes with alcohols saturated with dry hydrogen chloride causes the addition of the halogen acid to the double bond as well as acetalization to give /3-halo acetals. ... 

Unsymmetrical azines of an aromatic and an aliphatic carbonyl compound, such as benzophenone cyclohexanone azine, are reduced in slightly acidic solution with cleavage of the nitrogen-nitrogen bond and saturation of the aromatic azomethine group [Eq. (12)], whereas the aliphatic imine is then hydrolyzed [Eq. (13)] [48] unsymmetrical cyclic azines, such as 5-i/-2,3-benzodiazepines, are reduced similarly, usually with ring contraction. 

Blaser and Spencer used aroyl halides in place of aryl halides, with aroyl chlorides being of specific interest as ubiquitous, relatively cheap compounds ( Blaser reaction ) [24], This latter reaction is normally conducted in aromatic solvents phosphines are not used here as catalyst ligands since they fully inhibit the reaction. In the same way, benzoic acid anhydrides can be used as the aryl source in combination with PdCl2 and catalytic amounts of NaBr [79]. In this reaction, one of the arenes is used in the coupling reaction by elimination of CO, whereas the other benzoate serves as the base. The benzoic acid thus formed can easily be recycled into the anhydride. The use of aryl and vinyl triflates according to Cacchi [25] and Stille [26] extends the scope of the Heck coupling to carbonyl compounds phenol derivatives act via triflate functionalization as synthetic equivalents of the aryl halides. The arylation of cyclic alkenes [27], electron-rich vinyl ethers [28], and allylic alcohols [29] is accessible through Heck reactions. Allylic alcohols yield C-C-saturated carbonyl compounds (aldehydes) for mechanistic reasons (y9-H elimination), as exemplified in eq. (6). 

This reaction constitutes a method for the transformation of saturated cyclic or acyclic carbonyl compounds in three steps (silyl enol ether formation, halocarbene addition, rearrangement) to a,) -unsaturated carbonyl compounds with one-carbon ring enlargement or chain elongation, respectively. The rearrangement can be induced under acidic, basic, or thermolytic conditions, or with silver(I) salts. 

The carbonyl compounds that can undergo this condensation include aliphatic, aromatic, and <%,/ -unsaturated aldehydes, aliphatic, saturated carbo-cyclic, and aromatic ketones, diketones, oxo esters, and cyano ketones. Sodium ethoxide and potassium terf-butoxide are the condensing agents generally used. 

Although it is mentioned that cyclic acetals of saturated carbonyl compounds survive the LN treatment, those derived from phenones are susceptible, especially at higher temperatures (-40°C vs. —78°C). Actually both C-O bonds may be severed. ... 

Mixed coupling reactions, using two different carbonyl compounds, can be effected, but they generally lead to mixtures of products and are of limited use in synthesis. Intramolecular reactions with dicarbonyl compounds, on the other hand, provide a good route to cyclic alkenes. The keto-aldehyde 80, for example, gave the cyclic diterpene kempene-2, despite the presence of a saturated ketone... 

With saturated carbonyl compounds, and especially with aromatic carbonyl compounds, reaction between the photoexcited carbonyl chromophore and alkenes results in the formation of four-membered cyclic ethers (oxetane). The addition of carbonyl compounds to alkenes to give oxetanes is often referred to as the Patemo-... 

PhMe2Si)2CuLi undergoes l,4-(conjugate) addition to a variety of cyclic and acyclic a, 8-unsaturated enones to afford saturated 8-silyl carbonyl compounds (eq In acyclic... 

With Fe2(CO)9 as catalyst, the CDC reaction of saturated heterocycles with 1,3-diketones was accomplished using TBP as an eflhcient oxidant (Scheme 2.12) [48]. This protocol shows good compatibility to cyclic and acyclic ethers, thioe-thers, and tertiary amines. Gratifyingly, besides C(sp )-C(sp ) coupling, the oxidative C-N coupling of ethers with azoles also works well (Scheme 2.12) [49]. As a update, with 2-chloranil (tetrachloro-l,2-benzoquinone) as oxidant, benzyl thioethers can be employed as substrates under metal-free conditions [50]. Notably, 2,2,6,6-tetramethylpiperidine-l-oxoammonium tetrafluoro borate is also an effective oxidant for metal-free CDC reaction of isochromanes and carbonyl compounds [51, 52]. 

Lactones are cyclic esters derived from lactic acid (CsHeOs). They are constituents of many essential oils and plant volatiles. They contain a heterocyclic oxygen next to a carbonyl function in a five or more membered ring that is saturated or unsaturated. Those with a five-membered ring are called y-lactones, e.g. y-angel-ica lactone 148, whereas compounds containing a six-membered ring are called (5-lactones, e.g. (5-valerolactone 149 (Structure 4.45) [1-4, 6, 9, 22, 23,29, 62]. 

Remarkable chemoselectivities in acetalization of carbonyl groups promoted by microwave irradiation have been reported. For example, cyclic ketones can be selectively converted to their corresponding acetals, while acyclic ones remain unchanged under the same experimental conditions. Moreover, a,(3-unsaturated aldehydes and ketones react faster then the corresponding saturated compounds. 

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