Carbonyl unit

Poly(vinyl acetate). The dielectric and mechanical spectra of hybrids produced by mixing a poly(vinyl acetate)—THE solution with TEOS, followed by the addition of HCl have been investigated (45). Mixtures were made which were beheved to be 0, 5, 10, 15, and 20 wt % Si02, respectively. These composites were transparent and Eourier transform infrared spectroscopy (ftir) revealed hydrogen bonding between the siUcate network and carbonyl units of the poly(vinyl acetate) (PVAc). No shift in the T of the composites from that of the pure PVAc was observed. Similarly, the activation... 

On page 132, atropisomerism was possible when ortho substituents on biphenyl derivatives and certain other aromatic compounds prevented rotation about the bond. The presence of ortho-substituents can also influence the conformation of certain groups. In 88, R= alkyl, the carbonyl unit is planar with the trans C=0 - F conformer more stable when X=F. When X=CF3, the cis and trans are planar and the trans predominates. When R = alkyl there is one orthogonal conformation but there are two interconverting nonplanar conformations when R=0-alkyl. In 1,2-diacylbenzenes, the carbonyl units tend to adopt a twisted conformation to minimize steric interactions. " ... 

Catalysts have been developed that are compatible with both water and methanol. The reaction is compatible with the presence of other functional groups such as other alkene units,carbonyl units,and amides (see 125). ... 

Considering the isolobal relations between W(CO)5 or RSb, the complexes of type 29 and 30 may be considered as analogs of cvc/o-R3Sb3 or of complexes with a cyc/o-R3Sb3 ligand, which are still unknown. Closely related are the complexes [MeC(CH2Sb)3M(CO)5] (M = Cr, Mo, W)124 where a polycyclic tristibine is coordinated to metal carbonyl units. 

A one pot formation and purification of a 5-arylidine 4-thiazolidinone library has also been reported using polymer scavenging as the principle method of purification. An automated synthesizer was employed to make a parallel array of 4080 4-thiazolidinones, prepared simultaneously from a 3-component condensation of mercaptoacetic acid with an amine and a carbonyl compound. Further structural decoration was then introduced using the libraries from libraries principle where the core template was derivatized via an aldol reaction with a second carbonyl unit at the 5-methylene position (Scheme 2.57) [84]. After both synthetic steps. 

B. Where the paths are equal, such as in some nylons, the repeat unit is named so that the heteroatom N appears first and the more highly substituted (carbonyl) unit appears next. Thus nylon 3,3 with the structure... 

Dialkylboron trifluoromethanesulfonates (Inflates) are particularly useful reagents for the preparation of boron enolates from carbonyl compounds, including ketones, thioesters and acyloxazoiidinones. Recentiy, the combination of dicylohexyiboron trifluoromethanesulfonate and triethyiamine was found to effect the enolization of carboxyiic esters. The boron-mediated asymmetric aldoi reaction of carboxyiic esters is particuiariy usefui for the construction of anti p-hydroxy-a-melhyl carbonyl units. The present procedure is a siight modification of that reported by Brown, et ai. ... 

Alternatively, the displacement of alkoxide by attack of a nucleophile at the carbonyl unit of complexed magnesium S-ketoester can proceed smoothly according to a Claisen-type reaction, as described in the transformation of xantophanic enol 79 into resorcinol 80 (equation 101) . 

A pretty good diastereocontrol was achieved in the six-membered ring cyclization of 47, where diethylaluminium chloride and a catalytic amount of CuBr2 SMe2 were used to promote the internal attack of the Reformatsky centre to the sterically hindered carbonyl unit to give 48a and 48b (equation 32)108. 

In this work, studies were made on the photochemistry of styrene copolymers containing minor amounts (2-7%) of MVK, MIPK and tBVK. The properties of these polymers are summarized in Table I. The low concentrations of carbonyl units present should minimize the effects of energy... 

The reaction of 36 with carbon monoxide results in the formation of the neutral [Ira CO C/ -COX/ -C Xdppm ] 39, which, according to an X-ray crystallographic analysis, no longer contains an Ir—Ir bond [the M-M separation is 3.388(2) ]. This compound may be the first example of a compound that contains a five-membered metallocycle in which the -02- unit and the carbonyl unit are both bridging. 

The electronics and structure of the acceptors, especially a, 3-unsaturated ketones, is also a determinant in 1,2- vs. 1,4-addition processes. In general, substitution of aryl or large groups at the carbonyl unit increases the preference for 1,4-addition,16ab while a, 3-unsaturated aldehydes afford exclusive 1,2-addition and [3,(3-disubstitution suppresses 1,4-addition,l6c presumably due to steric hinderance. House and Seyden-Penne have established good correlations between chemoselectivity and either the half-wave electrolytic reduction potentials,17 or the energy levels of the LUMO of various a, 3-unsaturated ketones.17b... 

The use of masked acyl anion equivalents in a synthetic protocol requires additional steps to unmask the carbonyl unit. Sometimes the deprotection procedures are incompatible with sensitive compounds thus, a direct nucleophilic acylation protocol is desirable. While C-nucleophilic carbonyl groups do not... 

Both HRe(CO)s and H2Os(CO)4 can be oxidatively added to Os3(CO),, (NCMe) (126 -128). This leads to external attachment of the new metal carbonyl unit as in 64 (127), and a second HRe(CO)s molecule can be incorporated the same way (126). In both cases just one metal-metal bond has been formed in the first step. CO elimination from 64 introduces one more metal - metal bond, one possible result of which is rhomboidal 65 (126), whereas further CO elimination under H2 leads to full aggregation to tetrahedral 66 (127). All three steps of a M3 + M capping sequence have thereby been performed. A similar two-step sequence leads from Os6(CO)17(NCMe) and H2Os(CO)4 via H2Os7(CO)21 to H2Os7(CO)20 (128). 

The oligomer where Z = p-CeYh, reacted with Fe(CO)5 under UV irradiation to give an oligomer containing iron carbonyl units attached to ca 30% of the silole groups. 

We could look at every possible C-C carbonyl disconnection and decide which we prefer. For any even moderately complex molecule, this can be an exhausting process and we shall do it for just one target molecule. Thereafter we shall choose disconnections as we go along and go back to the target only if that strategy proves poor. Pratt and Raphael1 needed the keto-diester 1 for a synthesis of the anti-tumour compound vemolepin. Our first disconnection is easy as the a, 3-unsaturated carbonyl unit suggests the classic aldol la disconnection to 2. 

Formyl equivalents, such as DMF and triethyl ortfe-formate, are used to extend the acyl group of ortfe-hydro-xyacetophenoes by one carbonyl unit, which upon cyclization form chromones that are unsubstituted at C-2 <1984CFlEC, 1996CHEC-II>. Dimethylaminodimethoxymethane can react with l-(2-hydroxyphenyl)-3-phenylpro-pan-l-ones to afford homoisoflavones that are unsubstituted at C-2 (Equation 306) <2005SC563>. 

Scheidt et al. [62] reported the formation of saturated esters utilizing benzimi-dazolium salts when protonating the intermediate 67 (see Scheme 9.19) and trapping the resulting activated carbonyl unit with an alcohol nucleophile (Scheme 9.21). These authors were able to show that the electrophile (phenol) and the nucleophile (primary or secondary alcohols) can be decoupled, enabling a broad substrate scope, though they had to employ an excess of phenol (2 eq.) and the nucleophile (5 eq.), accompanied by rather harsh conditions (100 °C). 

Figure 7.3 Unlike most carbonyl-based functional groups, nonconjugated esters can react with nucleophiles and retain the carbonyl unit.

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