Aldehyde from acyl chlorides

More recently the acylation of aldehyde enamines has been reinvestigated (75) and shown to proceed normally when the enamine is added to the acid chloride. The morpholine enamine of isobutyraldehyde (98), on being added to an ether solution of acetyl chloride, afforded the iminium salt (99), from which the ketoaldehyde (100) was obtained in 66% yield by hydrolysis (75). 

As noted earlier, [HCr(CO)5] also converts alkyl halides to alkanes, but the reactivity of the acyl chloride is much higher, such that it was possible to selectively convert the acyl chloride to an aldehyde in one step, without interference from the alkyl bromide functionality. A second equivalent of [HCr(CO)5] further reduced the alkyl bromide (Eq. (27)). 

The same strategy has been used by Williams (90JA808) in his synthesis of brevianamide B. The aldehyde (82), prepared enantioselectively from L-proline, was converted to the silyl ether. Acylation of this (BuLi, ClC02Me) gave the carbomethoxy derivative as a mixture of diastereo-mers, which was alkylated by gramine. As before, an enolate alkylation (Sn2 ) on an allyl chloride derived from the above gave the tricyclic compound, which could be transformed to brevianamide B (Scheme 24). 

Silyl enolates react with acyl cation equivalents to give the C- and/or O-acylated products (Equation (90)).333 Fluoride-catalyzed reaction using acyl fluorides is valuable for O-acylation of silyl enolates derived from aldehydes and ketones.334 CuCl also promotes the 0-acylation with acyl chlorides.335 The CuCl-promoted reaction of ester silyl enolates results in exclusive (7-acylation. Combined use of BiCfl and Znl2 (or Nal) effects catalytic (7-acylation of ketone silyl enolates with acyl chlorides. 

Indium trichloride promotes catalytically the addition of alkynylstannanes to aldehydes (Table 25).42 Metallic indium also mediates the same Barbier-type coupling between alkynyl halides and aldehydes or ketones to give secondary or tertiary propargyl alcohols (Table 26). Secondary alcohols can be oxidized in situ according an Oppenauer process.395 Thus, alkynyl ketones have been prepared from aldehydes via an indium-mediated alkynylation reaction followed by an indium-mediated Oppenauer oxidation. They are also obtained via an indium-mediated alkynylation of the relevant acyl chlorides (Table 27).396... 

The procedure shown here describes the preparation of a-silyl ketones from aldehydes and acyl chlorides. The a-silyl ketones undergo Cram addition of various nucleophiles to produce diastereoselectively p-hydroxysilanes. These compounds are then subjected directly to elimination in situ under basic or acidic conditions to produce the corresponding alkenes. 

As acyl chlorides are the most reactive of the common acid derivatives, it is not surprising that they are the easiest to reduce. All the reducing methods described in the rest of this chapter are, in a sense, methods for the reduction of acyl chlorides, as they all involve derivatives which can be made from acid chlorides. Moreover, it is possible to find reducing systems sufficiently mild to convert the acyl chlorides directly to aldehydes without then reducing the aldehydes to alcohols. 

The mechanism of action of these metal hydrides is somewhat uncertain. In the original report on [HFe(CO)4]", it was suggested that, by analogy with [Fe(CO)4], the anion displaces a chloride ion from the acyl chloride to give an intermediate (17) which then collapses to give the aldehyde (Scheme 7). However, there are alternative possibilities, particularly that the reagents act as H-atom donors (like... 

The McFadyen-Stevens aldehyde synthesis - is based on the reaction shown in Scheme 13, in which arenesulfonylhydrazides (40) are decomposed to aldehydes by treatment with base. It is generally presumed that the acylimides (41) are intermediates in the procedure. The arenesulfonylhydrazides can be synthesized either from acid hydrazides and arenesulfonyl chlorides or from acyl chlorides and arene-sulfonylhydrazines. The latter method is somewhat more common in recent work and is reported to give superior yields. ... 

Control in the selection of ring substituents is an important element of oxazole synthesis. This is a feature of a new route that employs 0-trimethylsilyl acyltrimethylsilane cyanohydrins (148), which are obtained from aldehydes or acyl silanes <92JOC333l>. These intermediates, which provide the C-5 substituent and four of the five ring atoms, are reacted sequentially with organolithium reagents (C-4 substituent) and acyl chlorides or anhydrides (C-2 substituent) to furnish, -bis(trimethylsilyl) enamines (149), which cyclize under thermal conditions or upon treatment with trimethylsilyl trilluoromethanesulfonate (Scheme 68). The range of oxazoles accessible by this method includes those with alkyl, alkenyl, phenyl, and functionalized substituents at C-2, alkyl, alkenyl, and phenyl substituents at C-4, and alkyl and phenyl substituents at C-5. The rare 4-(, -dialkylamino)oxazoles (150) may also be prepared. 

This chapter will revisit the lUPAC nomenclature system for aldehydes, ketones, and carboxylic acids, as well as introduce nomenclature for the four main acid derivatives acid chlorides, anhydrides, esters, and amides. The chapter will show the similarity of a carbonyl and an alkene in that both react with a Br0nsted-Lowry acid or a Lewis acid. The reaction of a carbonyl compound with an acid will generate a resonance stabilized oxocarbenium ion. Ketones and aldehydes react with nucleophiles by what is known as acyl addition to give an alkoxide product, which is converted to an alcohol in a second chemical step. Acid derivatives differ from aldehydes or ketones in that a leaving group is attached to the carbonyl carbon. Acid derivatives react with nucleophiles by what is known as acyl substitution, via a tetrahedral intermediate. 

The reaction of trialkyl phosphites with aldehydes or ketones in the presence of hydrogen chloride gives dialkyl-1-hydroxy alky Iphosphonates via Arbuzov-type reactions of oxonium salts derived from aldehydes or ketones. This reaction is an alternative to the Abramov reaction.Reduction of activated carbonyl groups, such as a-ketophosphonates by alkyl phosphine, afforded the corresponding reduced products. A new monomer, N-acyl pamidronate (152), which copol5merizes with N-isopropylamide provides a cross linked hydrogel (153) that serves as a substrate for direct biomineralization e.g. the formation of hydroxyapatites). 

A novel strategy for the synthesis of pyridines from aldehyde, enam-ide, and isonitrile was described by Wang and coworkers in 2013 [122], The reaction works under mild reaction conditions and good to excellent yields can be achieved. Mechanistically, this cascade reaction consisted by Zn(OTf)2-promoted [1 + 5] cycloaddition of isonitrile with A-formylmethyl-substituted enamide, facile aerobic oxidative aromatization and intermolecular acyl transfer from the pyridinium nitrogen to the 5-hydroxy oxygen, and finally acylation of the 4-amino group by an external acyl chloride efficiently afforded 2-substituted 4-acylamino-5-acyloxypyridines. 

The electron-withdrawing rerr-butoxy groups decrease the reactivity of the A1—H bond. As a result, hthium tri(rerr-butoxy)aluminum hydride displaces a chloride ion from an acyl chloride, but will not reduce the carbonyl group of the aldehyde. By contrast, lithium aluminum hydride reduces acyl... 

Chiral 2-oxazolidones are useful recyclable auxiliaries for carboxylic acids in highly enantioselective aldol type reactions via the boron enolates derived from N-propionyl-2-oxazolidones (D.A. Evans, 1981). Two reagents exhibiting opposite enantioselectivity ate prepared from (S)-valinol and from (lS,2R)-norephedrine by cyclization with COClj or diethyl carbonate and subsequent lithiation and acylation with propionyl chloride at — 78°C. En-olization with dibutylboryl triflate forms the (Z)-enolates (>99% Z) which react with aldehydes at low temperature. The pure (2S,3R) and (2R,3S) acids or methyl esters are isolated in a 70% yield after mild solvolysis. 

The chemistry of the carbonyl group is probably the single most important aspect of organic chemical reactivity Classes of compounds that contain the carbonyl group include many derived from carboxylic acids (acyl chlorides acid anhydrides esters and amides) as well as the two related classes discussed m this chapter aldehydes and ketones... 

V-Acylation of oxaziridine (54) is of more importance, yielding 2-acyloxaziridines which were unaccessible otherwise until recently. Oxaziridines (54) derived from cyclohexanone, butanone or benzaldehyde are acylated readily by acetic anhydride, acid chlorides or isocyanates. Oxaziridines from aliphatic aldehydes, too unstable to be isolated, may be trapped in situ by benzoylation (67CB2593). 

Synthesis of the remaining half of the molecule starts with the formation of the monomethyl ether (9) from orcinol (8). The carbon atom that is to serve as the bridge is introduced as an aldehyde by formylation with zinc cyanide and hydrochloric acid (10). The phenol is then protected as the acetate. Successive oxidation and treatment with thionyl chloride affords the protected acid chloride (11). Acylation of the free phenol group in 7 by means of 11 affords the ester, 12. The ester is then rearranged by an ortho-Fries reaction (catalyzed by either titanium... 

---