Cross carbonylative

Cyclopropenones and carbon monoxide react in the presence of Ru3(CO)12 to form tetrasubstituted pyranopyr-andiones 655 in high yield (Equation 266) <2002JA6824>. Unsymmetrical tetrasubstituted pyranopyrandiones 656 can be accessed by the cross-carbonylation of cyclopropenones and internal alkynes in the presence of a ruthenium catalyst (Equation 267) <2002JA6824>. 

The reaction was extended to the cross-carbonylation of cyclopropenones and internal alkynes, leading to unsymmetrically substituted pyranopyrandiones (Eq. 18) [33]. 

The 3,4-dioxoperhydro derivative of (3) was obtained by cross carbonylation of 2-hydroxymethyl-pyridine <87CC125>. Reaction of Schiff bases, prepared from 2-aminopyridine and its 5,6-benzologue with aldehydes and dichlorocarbene, afforded 2-aryl-3-chloro-4-oxo-4/f derivatives of (12) and its 6,7-benzologue <9lKGS8io>. 

Satoh, T., Itaya, T., Okuro, K. et al. (1995) Palladium-catalyzed cross-carbonylation of aryl iodides with five-membered cyclic olefins. J. Org. Chem., 60, 7267-71. 

Treatment of dialkylcyclopropenones with catalytic amounts of Ru3(CO) 2 and EtgN under CO resulted in carbonylative dimerization of cyclopropenones to give pyranopyrandiones in good yields (Scheme 2.111) [169]. Cross-carbonylation of dipropylcyclopropenone with dec-5-yne resulted in unsymmetrically substituted pyranopyrandione 148. 

In most cases, the proteia is immobilized onto y-aminopropyl sUica and covalently attached usiag a cross-linking reagent such as -carbonyl diimidazole. The tertiary stmcture or three dimensional organization of proteias are thought to be important for their activity and chiral recognition. Therefore, mobile phase conditions that cause proteia "deaaturatioa" or loss of tertiary stmcture must be avoided. 

Bulk Polymerization. The bulk polymerization of acryUc monomers is characterized by a rapid acceleration in the rate and the formation of a cross-linked insoluble network polymer at low conversion (90,91). Such network polymers are thought to form by a chain-transfer mechanism involving abstraction of the hydrogen alpha to the ester carbonyl in a polymer chain followed by growth of a branch radical. Ultimately, two of these branch radicals combine (91). Commercially, the bulk polymerization of acryUc monomers is of limited importance. 

Moderate yields of acids and ketones can be obtained by paHadium-cataly2ed carbonylation of boronic acids and by carbonylation cross-coupling reactions (272,320,321). In an alternative procedure for the carbonylation reaction, potassium trialkylborohydride ia the presence of a catalytic amount of the free borane is utilized (322). FiaaHy, various tertiary alcohols including hindered and polycycHc stmctures become readily available by oxidation of the organoborane iatermediate produced after migration of three alkyl groups (312,313,323). 

AldolRea.ctlons, In the same way, hydroxybenzaldehydes react readily with aldehydes and ketones to form a,P-unsaturated carbonyl compounds in the Claisen-Schmidt or crossed-aldol condensation (60). 

The cross-conjugated system of two a,P-unsaturated carbonyl groups of both 1,2- and 1,4-quinones occurs in many polynuclear hydrocarbons, eg, 1,2-naphthoquinone [524-42-5] (8) and 1,4-naphthalenedione [130-15-4] (1,4-naphthoquinone) (9) (see Fig. 1). The carbonyl groups may be located in different rings, but occupy positions corresponding to the 1,2- or 1,4-orientation of monocyclic quinones, eg, in naphthalenes such as 2,6-naphthoquinone... 

Proliferous Polymerization. Eady attempts to polymerize VP anionicaHy resulted in proliferous or "popcorn" polymerization (48). This was found to be a special form of free-radical addition polymerization, and not an example of anionic polymerization, as originally thought. VP contains a relatively acidic proton alpha to the pyrroHdinone carbonyl. In the presence of strong base such as sodium hydroxide, VP forms cross-linkers in situ probably by the following mechanism ... 

Cross-linked PVP can also be obtained by cross-linking the preformed polymer chemically (with persulfates, hydrazine, or peroxides) or with actinic radiation (63). This approach requires a source of free radicals capable of hydrogen abstraction from one or another of the labile hydrogens attached alpha to the pyrrohdone carbonyl or lactam nitrogen. The subsequently formed PVP radical can combine with another such radical to form a cross-link or undergo side reactions such as scission or cyclization (64,65), thus ... 

Interesting structures can be formed by combinations of ring and side-chain substituents in special relative orientations. As indicated above, structures (28) contain the elements of azomethine or carbonyl ylides, which are 1,3-dipoles. Charge-separated species formed by attachment of an anionic group to an azonia-nitrogen also are 1,3-dipoles pyridine 1-oxide (32) is perhaps the simplest example of these the ylide (33) is another. More complex combinations lead to 1,4-dipoles , for instance the pyrimidine derivative (34), and the cross-conjugated ylide (35). Compounds of this type have been reviewed by Ramsden (80AHCl26)l). 

Ozone cracking is a physicochemical phenomenon. Ozone attack on olefinic double bonds causes chain scission and the formation of decomposition products. The first step in the reaction is the formation of a relatively unstable primary ozonide, which cleaves to an aldehyde or ketone and a carbonyl. Subsequent recombination of the aldehyde and the carbonyl groups produces a second ozonide [58]. Cross-linking products may also be formed, especially with rubbers containing disubstituted carbon-carbon double bonds (e.g. butyl rubber, styrene-butadiene rubber), due to the attack of the carbonyl groups (produced by cleavage of primary ozonides) on the rubber carbon-carbon double bonds. 

While the usual eonsequence of hydration of enamines is eleavage to a secondary amine and an aldehyde or ketone, numerous cases of stable carbinolamines are known (102), particularly in examples derived from cyclic enamines. The selective terminal hydration (505) of a cross-conjugated dienamine-vinylogous amide is an interesting example which gives an indication of the increased stabilization of the vinylogous amide as compared to simple enamines, which is also seen in the decreased nucleophilicity of the conjugated amino olefin-carbonyl system. 

The mechanism of the Patemo-Biichi reaction is not well understood, and while a general pathway has been proposed and widely aceepted, it is apparent that it does not represent the full scope of reactions. Biichi originally proposed that the reaction occurred by light catalyzed stimulation of the carbonyl moiety 1 into an excited singlet state 4. Inter-system crossing then led to a triplet state diradical 5 which could be quenched by olefinic radical acceptors. Intermediate diradical 6 has been quenched or trapped by other radical acceptors and is generally felt to be on the reaction path of the large majority of Patemo-Biichi reactions. Diradical 6 then recombines to form product oxetane 3. 

In contrast to the saturated azlactones, the Friedel-Crafts reaction of 2-substituted-4-arylidene-5-oxazolones is quite complex and may follow several different courses, often concurrently, depending on both reaction conditions and structural variations in the arylidene ring. This behavior is readily interpreted in terms of the a,)S-unsaturated carbonyl moiety and the cross-conjugated system containing nitrogen, both of which provide potential reaction sites in addition to the lactone carbonyl group. The reaction has been investigated " ... 

From a mixture of two different aldehydes, each with a-hydrogens, four different aldols can be formed—two aldols from reaction of molecules of the same aldehyde -I- two crossed aldol products not even considering possible stereoisomers (see below). By taking into account the unsaturated carbonyl compounds which could be formed by dehydration from the aldols, eight different reaction products might be obtained, thus indicating that the aldol reaction may have preparative limitations. 

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