Anions acylation

Indolo[2,3-d][l,3]thiazine-2,4-dithione formation, 4, 299 Indolothiazines synthesis, 4, 519 Indoloyl azides Curtius rearrangement, 4, 288 Indolyl anions acylation, 4, 232 alkylation, 4, 235 Michael-type additions, 4, 236 Indomethacin... 

Nucleophilic acyl complexes can be 0-alkylated with hard electrophiles to yield the corresponding alkoxy- or (acyloxy)carbene complexes. The first carbene complex ever isolated [61] was prepared by this route the intermediate, anionic acyl complex was generated by addition of phenyllithium to tungsten hexacarbonyl (Figure 2.3). 

In the first, Fe(CO)5 is converted into the carbonyl hydride anion by reductive decarboxylation following initial OH" attack on a carbonyl carbon (55). The carbonyl group is thus oxidized to carbonate in basic medium. The second reaction, (3) (56), is one of E. O. Fischer s celebrated carbene forming reactions (57). Phenyl lithium reacts with Cr(CO)6 leading to an anionic acyl complex. A subsequent alkylation step using Me30+ yields the methoxy-phenylcarbene complex Cr(CO)5(CPh(OMe)). 

The iodide complexes, [CpMo(CO)3 (CH2)3I ] [M = Mo (96) or W (97)], were originally prepared by Winter and co-workers (162). Both 96 and 97 react with excess iodide to form [CpMfCOJjIfCOfCH CHj ]. Winter and co-workers found that transition metal anions may induce similar cyclization reactions. Hence, reaction of excess Na[CpMo(CO)3] with Br(CH2)3Br yields 89, which reacts with further Na[CpMo(CO)3] to form an intermediate anionic acyl complex, which in turn undergoes elimination of Br- to form the carbene ligand in a manner similar to that... 

Anionic acyl-iron complex (8) may be intercepted by ethylene, which inserts into the acyl-iron bond to produce a S-metalloketone that rearranges to an a-metalloketone (Scheme 4). Protonation affords the ethyl ketone. Intramolecular (see Intramolecular) versions of this process are known as well, and provide an approach to cychc ketones. That the cyclization is not always regioselective (see Regioselectivity) is shown in an example used in the total synthesis of ( )-aphidicolin (Scheme 5). 4i... 

The anion [36p (R = Ph) oxidatively adds alkyl halides, RX, to give the anionic acyl complexes 37 (55). 

Although a variety of new preparative routes has been developed in recent years (for reviews see refs 1 -10), the transformation of the metal-carbonyl carbon bond of a metal-carbonyl complex into a metal-carbene carbon bond is still the most useful and versatile method for preparing transition-metal carbene complexes. The addition of a carbanion to the carbon atom of a carbonyl ligand yields an anionic acyl complex that subsequently can be reacted with an electrophile to give a neutral carbene complex. Thus, the syntheses of anionic acyl and neutral carbene complexes are closely related, for almost all the carbene complexes considered in this section acyl complexes are precursors, although most have not been isolated and characterized. The syntheses of acyl complexes via CO insertion (for reviews see refs. 11, 12) or by reaction of metal carbonyl anions with acyl halides is outside the scope of this section. 

The formation constants of an actinium isopropyltropolonate complex were determined. Thermochemically relevant studies of thorium enolates generally involve bis(pentamethyl-cyclopentadienyl)thorium derivatives. Cp 2Th(Cl)(C(0)CFl2Bu-f) with an anionic acyl group that readily rearranges to the isomeric enolate Cp 2Th(Cl)OCH=CHBu-t. The Z-isomer is formed upon heating and the -isomer upon catalysis with Cp 2ThH2. Is the E or Z enolate thermodynamically more stable For the simple alkyl enolates MeCH=CHOR, the equilibration reaction of the Z- and E-isomers is nearly thermo-neutral . Consider the two species Cp 2Th(H)OCH(Bu-t)2 and Cp 2Th(H)0-2,6-C6H3 (Bu-f)2. The reversible addition of CO yields the rp- formyl derivative in reactions that are 19 4 and 25 6 kJmoR exothermic. These formyl species dimerize to form the classical enediolate, Cp 2Th(OR)OCH=CHO(OR)ThCp 2. This product is formed as the Z-isomer, plausibly thermodynamically preferred over the -isomer, much as (Z)-MeOCH=CHOMe is preferred over its E-counterpart by 6.0 0.2 kJmoR. ... 

There have also been a few examples of ring expansions involving azetines. One such instance, which follows a pericyclic mechanism, is the thermolysis of 4-cyano-l-t-octyl-3-t-octylamino-2-t-octyliminoazetine (160), producing the 4-amino-5-cyanoimidazole (Scheme 89). Such azetine species have been implicated as intermediates in the photolysis of enaminonitriles to imidazoles (Section 4.08.1.1.1 Scheme 17). In strongly basic medium the azetidinone (161), which possesses a lactam group, is ring expanded to the 4H-imidazolinone (163), probably via the anionic acylic species (162 Scheme 89) <80AHC(27)241>. 

Reaction with germyllithiutn reagents can yield CO inserted products (92) [Eq. (54)]. Thus methyl rheniumpentacarbonyl reacts with germyl-lithium compounds to give anionic acyl complexes which can be isolated as tetraethylammonium salts or alkylated to give carbene complexes. 

The first step involves formation of an anionic acyl complex, which then undergoes intramolecular SN2 displacement of bromide to yield 23. 

When the aldol strategy is ideal When the aldol strategy is not ideal Symmetry as a guide Wittig-style aldol methods Strategy 4b Acylation of a Vinyl Anion Vinyl metal reagents The aliphatic Friedel- Crafts reaction Unsaturated Acyl Cations and Anions Acyl anion equivalents (d1 reagents)... 

Anion (1) is a strong nucleophile. Reaction (e) has been reported attack on the anionic acyl derivative gives aldehydes, similar to the already encountered reaction of [Cr(CO>5COR] anions with protons ... 

When carbon monoxide is bonded to a transition element, in a positively charged or even uncharged compound, the electrophilic capacity of carbon increases compared with the isolated molecule. Examples of nucleophilic attack are in equations (4) and (5). The reaction of methyl-lithium with W(CO)e giving the anionic acyl complex of equation (4a) is followed by alkylation to the carbene derivative of equation (4b). The formation of a carbamoyl complex with c/5-PtCl2(CO)2 is shown in equation (5). 

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