Miscellaneous reactions reaction with acetals

Miscellaneous Compounds. A saturated spirocychc pyrrohdine serves as the nucleus for a diamine that has been described as a hypohpemic agent. Treatment of the carbanion of the substituted cylcohexane carboxyhc ester (20-1) with methyl bromoacetate leads to the alkylation and formation of the diester (20-2). Saponification of the ester groups followed by reaction with acetic anhydride leads to ring closure of the succinic anhydride (20-3). Condensation with ammonia leads to the succinimide (20-4). The side chain is then added by alkylation of the anion on nitrogen with l-bromo-4-dimethylaminobutane (20-5). Reaction of this last intermediate with lithium aluminum hydride leads to the reduction of the carbonyl groups to methylene. This affords the pyrrolidine (20-6) atiprimod [22]. 

A number of miscellaneous reactions involving diazonium ions and possible vinyl cations have been reported. Treatment of amine 138 with sodium nitrite in 20% aqueous acetic acid is reported to give methyl cyclopropyl ketone as one of four products (116). The reaction has been postulated to involve a vinyl cation, presumably by the following sequence of reactions (116) ... 

Miscellaneous Reactions.—Trity fluoroborate. previously reported as cleaving acetals by hydride abstraction, also cleaves benzylic ethers and a variety of related species, giving benzaldehydes. " Cholesteryl benzyl ethers afford cholesterol. The bismethylenedioxy protecting group for the corticosteroid side-chain is also cleaved with this reagent. 

Miscellaneous Reactions. In addition to the key reactions above, DDQ has been used for the oxidative removal of chromium, iron, and manganese from their complexes with arenes and for the oxidative formation of imidazoles and thiadia-zoles from acyclic precursors. Catal)ftic amounts of DDQ also offer a mild method for the oxidative regeneration of carbonyl compounds from acetals, which contrasts with their formation from diazo compounds on treatment with DDQ and methanol in nonpolar solvents. DDQ also provides effective catalysis for the tetrahydropyranylation of alcohols. Furthermore, the oxidation of chiral esters or amides of arylacetic acid by DDQ in acetic acid provides a mild procedure for the synthesis of chiral a-acetoxy derivatives, although the diastereoselectivity achieved so far is only 65-67%. ... 

The Lewis acid-mediated coupling of alkyl enol ethers with acetals was discovered in 1937 by Martin Muller-Cunradi (1902-1945) and Kurt Pieroh at BASF, and is one of the lesser-known key reactions in the chemistry of carotenoids it can be employed in miscellaneous ways and repeatedly for the construction of complex structures. [64]... 

Miscellaneous Fused Selenophens.—Selenolo[2,3-6]thiophen (691) has been prepared by metalation of thiophen>3-aldehyde diethyl acetal with butyl-lithium followed by reaction with selenium and methyl chloroacetoacetate. The intermediate (692) was, without isolation, hydrolysed and ring-closed to (693), which upon decarboxylation gave (691). Another isomeric... 

P-keto-acids, and the saponification of only one cyano-function in the reaction with malononitrile is difficult to rationalise. Treatment of compounds containing active methylene groups with cupric acetate in the presence of an alkene can lead to a cyclopropane (8—66%) by a radical route.1,3-Debromination, by sodium, of suitable precursors has led to a series of new spirans, and a new synthesis of cyclopropane from 3-bromopropyne and allylic zinc bromides has been claimed. Miscellaneous Methods.—Pyrolysis of (144) leads to carbonylcyclopropane, which undergoes ready dimerization on warming to ambient temperatures. The ketone... 

Miscellaneous Reactions.—second method for the oxidative decarboxylation of acids has appeared this year see also ref. 335. Thus, 5-cndo-norborn-2-ene carboxylic acid on conversion to its dianion and reaction with molecular oxygen affords the a-hydroperoxide. The hydroperoxide is decomposed to 5-norbomen-2-one by reaction with p-toluenesulphonic acid or by reaction with dimethylformamide dimethyl-acetal. 

Miscellaneous Reactions. Primary allylic alcohols can be prepared readily by the action of p-toluenesulfonic acid in acetic anhydride-acetic acid on the corresponding tertiary vinyl carbinol, followed by hydrolysis of the resulting acetate. The vinyl carbinol is readily available from the reaction of a ketone with a vinyl Grignard reagent. Overall yields of allylic alcohols are very good (eq 50). 

Miscellaneous Reactions. DTBP has been used as a hydrosi-lylation catalyst, even though catalysis by transition metal complexes have largely replaced the radical methods. DTBP has also been used as an oxidant for silanes. Other applications of DTBP include its use as an initiator for radical mediated deoxygenation of alcohols via the corresponding chloroformate or acetate ester (eq 20). It has also been used as an initiator for the reduction of lactones and esters to ethers using trichlorosilane. In a rare example of a nonradical reaction, DTBP has been used in conjunction with titanium(IV) chloride for the formation of chlorohydrin from alkenes (eq 21). ... 

Miscellaneous Reactions. MTO finds an interesting application in the peroxyacetalization of ketones, aldehydes, and acetals with H2O2 as the oxidant, 1,1-dihydroperoxides are obtained (eq 63). ... 

Miscellaneous Reactions. DMF acetals catalyze rearrangement reactions of allylic alcohols to p,7-unsaturated amides. This reaction, which involves a [2,3]-sigmatropic rearrangement, occurs with complete transfer of chirality. Thus the reaction of the (/ ,Z)-allylic alcohol (eq 15) with DMF dimethyl acetal gives the enantiomerically pure (R, )-p,7-unsaturated amide as the only product. The (5, )-isomer also rearranges mainly to the (/ , )-amide, with only a trace of the (5,Z)-isomer. It has been suggested that both rearrangements proceed via a five-membered cyclic transition state with a carbene-like function. ... 

Miscellaneous Reactions. The coupling of silyl ketene acetals (enolsilanes) with pyridine derivatives bearing an electron-withdrawing substituent, namely cyano, in the meta position is catalyzed by iron montmorillonite and other similar solid-acid catalysts (eq 16). ... 

Several other miscellaneous heterogeneously catalyzed reactions have been performed in the liquid phase. Hexane was successfully oxyfunctionalized with aqueous hydrogen peroxide by use of the zeolite TS-1 catalyst [50] and microwave-promoted acetalization of a number of aldehydes and ketones with ethylene glycol proceeded readily (2 min) in the presence both of heterogeneous (acidic alumina) and homogeneous (PTSA, Lewis acids) catalysts [51], Scheme 10.7. 

Other miscellaneous syntheses that have benefited from the introduction of dppf to the catalytic mixture include the coupling reactions of aryl triflates or halides with ketene trimethylsilyl acetals [165], The catalyst mixture is [Pd(OAc)(i -C4H7)]2/LiOAc/phos-phine. In this case, nucleophilic activation of the Si-O bond of the acetal enables an Si-Pd transmetalation to give a a-complex 52 without necessitating a phosphine... 

Miscellaneous Methods of Preparing Phosphines. Palladium-catalysed formation of phosphorus-carbon bonds continues to be developed as a useful route to organophosphines. The reactions of primary or secondary phosphines with aryl- or vinyl-halides in the presence of a palladium catalyst, usually palladium acetate or a zerovalent palladium-phosphine complex, have been used in the synthesis of steroidal phosphines, e.g., (128), the cationic diphosphine system... 

A catalyst system159 consisting of a mixture of boron trifluoride, acetic acid and pyridine gives rapid and reproducible total hydroxyl analysis (silanol plus water) in a variety of silicone materials. This method avoids many of the interferences, empirical calibration and miscellaneous problems such as poor solubility, incomplete reaction and interfering siloxane cleavage associated with many earlier methods. Results obtained by this procedure compare well with results obtained by the lithium aluminium hydride procedure160. 

Miscellaneous Cycloadditions. The major reaction of alkyl- and aryl-substituted cyclopropenones with enamines to give amides involves formal C-1—C-2 bond cleavage of the cyclopropenone with cycloaddition to the enamine to give an initial dipolar intermediate (430). This mechanism also accounts for minor products. Work was extended to include reactions of enamines with diphenylcyclopropenethione and a re-evaluation of earlier evidence concerning reactions of diphenylcyclopropen-one and -thione with keten acetals. ... 

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