Reactions with carbonyl compounds olefin yields

Alkenyl sulfides are known to react with some labile electron-deficient olefins such as methyl vinyl ketone in the presence of AlCl3 to form cyclobutanes [25]. In the present chiral titanium-promoted asymmetric reaction, alkenyl sulfides can also be employed as electron-rich components. 2-Ethylthio-l-propene (7a) reacts with 2a in the presence of a catalytic amount of the chiral titanium reagent, giving the diastereomeric [2-1-2] cycloaddition products 8a and 9a in 51% (>98% ee) and 19% (79% ee) yields, respectively (Scheme 7 and Table 2). Although 2-ethylthio-l-propene (7a) is known as a good ene component in the reaction with carbonyl compounds, 3-(3-(methoxycarbonyl)-5-ethylthio-5-hex-enoyl)-l,3-oxazolidin-2-one, an ene product, is obtained only in 16% yield as a side product. 

Furan has been found to form oxetanes with a variety of carbonyl compounds, e.g., ketones,202-205 aldehydes,206 and ethyl cyanofor-mate.207 In most reactions the (2 + 2)-cycloaddition occurred specifically to give a 2,7 dioxabicyclo[3.2.0]hept-3-ene (175) rather than the 2,6-isomer (176). Only the addition of ethyl cyanoformate yielded mixtures of 175 and 176 (R = OEt and R2 = CN), in a ratio of 2 l.207 Two subsequent (2 + 2)-cycloadditions of benzophenone and furans have been reported to give two isomeric products, 177 and 178.205 Substituted furans yielded similar oxetanes.203 Benzo[ >]furans, furo-coumarins, and furochromones also proved to undergo (2 + 2)-cyclo-addition reactions with carbonyl compounds such as ketones, aldehydes, and quinones. Invariably one type of oxetane was formed (179).,37,u3 ,44 200-202 208,20, In the case of 2-methoxycarbonylbenzo[6)-furan, evidence has been provided that the oxetane was produced by addition of the excited triplet state of the olefinic reactant to the ground state of the ketone.208... 

Sodium acetylide (prepared from sodium amide) is useful for the condensations with primary alkyl halides. However, secondary, tertiary, and primary halides branched at the second carbon atom are dehydrohalogenated to olefins by the reagent. Iodides react at a faster rate than bromides and the latter faster than chlorides. Chlorides are rarely used. The bromides are more common for preparative reactions. Sodium acetylide can also react with carbonyl compounds to yield acetylenic carbinols. 

The photocycloaddition of an aldehyde or ketone with an olefin to yield an oxetane was reported by Paterno and Chieffi in 1909. 58> Contemporary studies on the synthetic utility and mechanistic features were initiated nearly 50 years later by Biichi et al. 59) Two review articles summarizing synthetic aspects of Paterno-Biichi reactions have been published 6.12)) and mechanistic studies have been reviewed several times. 6,38,60-62) The reaction involves the addition to olefin of a photo-excited carbonyl moiety. This circumstance makes it advantageous to review this reaction before a discussion of olefin-olefin additions, because the solution photochemistry of carbonyl compounds is probably better understood than any other aspect of organic photochemistry. Many of the reactions of carbonyl compounds have been elucidated during studies of the important phenomena of energy transfer and photosensitization. 63-65)... 

Trippett and Walker (97) found that the reaction of para-substituted benzylidene triphenylarsoranes with carbonyl compounds led to olefins when the benzylidene para substituent is highly electron withdrawing, but otherwise to epoxide. KumaricY al. (64) prepared two new semistabilized arsonium ylides, p-bromo- and p-iodobenzylidene triphenylarsorane, which were treated with a series of carbonyl compounds to yield exclusively trans-olefins. In no case was an epoxide obtained. 

At this point it should be noted, that olefination involving reaction of PO-stabilized carbanions like those from phosphonates, phosphinates, phosphine oxides, phos-phonamides or thiophosphonates (Horner reaction 47), Horner-Wadsworth-Emmons reaction48 ) with carbonyl compounds almost exclusively yields ( )-olefins. This olefination is essentially restricted to PO-activated compounds carrying stabilizing groups on the carbanionic C-atom. However, these compounds are more reactive than the corresponding resonance-stabilized ylides. Therefore, this olefination method... 

Thus, reactions of carbonyl compounds with hydrogen peroxide and acids lead to products similar to those obtained by the ozonization of olefins (Section III), which also yields 1,2,4-trioxolans and 1,2,4,5-tetroxans. The similarity of the two reactions is understandable, since the intermediates )C+—OO- in the ozonization27a and )C+—OOH in the hydrogen peroxide reactions are related as a conjugate base-acid pair. A number of cyclic peroxides of structure 7 are prepared from bis(hydroperoxy)dialkyl peroxides (5) by reaction with lead(IV) acetate, as described by Criegee et al.la This reaction is also thought to involve a carbonium ion intermediate,31 which reacts with the second OOH group. 

The main-stream reactions of metalated heterocyclic sulfones with carbonyl compounds afford the respective olefins in high yields. However, important side reactions were recorded. 

The olefination based upon the reaction of benzothiazolyl- and phenyltetra-zolyl sulfones with carbonyl compounds is widely used in the target-oriented synthesis. In order to illustrate the reaction scope, yields and stereoselectivities, in this section we present selected examples of these reactions. The examples include reactions of saturated sulfones with saturated aldehydes, saturated sulfones with o, j6-unsaturated carbonyl compounds, -unsaturated sulfones with saturated aldehydes, and /l,y-imsaturated sulfones with a, -unsaturated aldehydes. The emphasis is given to recent work. A complete account of earlier applications of the modified Julia reaction has been given in the Blakemore review [98]. 

Peterson reaction (olefination). Reaction of a-silylated carbanions with carbonyl compounds, yielding (3-hydroxyl-alkyl silanes, which undergo instantaneous elimination to afford olefins. 

The reaction of phosphorus ylides with carbonyl compounds as a route to fluoro-olefins is prone to complications (see Vol. 2, p. 46), but excellent yields of olefins are obtained upon dehalogenation of fluoroiodomethyltriphenylphos-phonium iodide with zinc-copper couple, e.g, ... 

Polyenephosphonium halides can also be reacted with carbonyl compounds in a variant of the Wittig reaction [89] in which oxiranes function as hydrogen halide acceptors. Carbonyl olefination of 79 with 58 in butylene oxide readily leads to 406, which is isolated as described above, in a yield of 83%. 

The synthesis of a-fluorovinylsulfones by the use of the Peterson olefination has been described by Usuki et al. who reacted silyl lithiums 86 generated in situ from the corresponding ot-fluoro-a-silyl sulfones 85 and TBSCl, with carbonyl compounds 87. They found that the reaction proceeded in better yield when an aldehyde was used rather than a ketone. The phenylsulfonyl moiety could be reductively removed using a sodium amalgam in NaH2P04-NaHP04. 

Two groups have developed means of extending the condensation of sulphinyl carbanions with carbonyl compounds, such that it becomes an alternative to the Wittig reaction, through conversion of the initial carbinol adducts into olefins. Dimsyl-lithium with benzophenone gave the initial adduct as a lithium salt, which, when treated with a chlorophosphite at -80 °C, afforded a 91% yield of diphenylethylene." The isolated initial adduct (97) could be converted into undecene by reaction first with MeS—CH CH—(CH2)sCH3... 

The Julia-Lythgoc olefination operates by addition of alkyl sulfone anions to carbonyl compounds and subsequent reductive deoxysulfonation (P. Kocienski, 1985). In comparison with the Wittig reaction, it has several advantages sulfones are often more readily available than phosphorus ylides, and it was often successful when the Wittig olefination failed. The elimination step yields exclusively or predominantly the more stable trans olefin stereoisomer. 

These reversible reactions are cataly2ed by bases or acids, such as 2iac chloride and aluminum isopropoxide, or by anion-exchange resias. Ultrasonic vibrations improve the reaction rate and yield. Reaction of aromatic aldehydes or ketones with nitroparaffins yields either the nitro alcohol or the nitro olefin, depending on the catalyst. Conjugated unsaturated aldehydes or ketones and nitroparaffins (Michael addition) yield nitro-substituted carbonyl compounds rather than nitro alcohols. Condensation with keto esters gives the substituted nitro alcohols (37) keto aldehydes react preferentially at the aldehyde function. 

Such copolymers of oxygen have been prepared from styrene, a-methylstyrene, indene, ketenes, butadiene, isoprene, l,l-diphen5iethylene, methyl methacrjiate, methyl acrylate, acrylonitrile, and vinyl chloride (44,66,109). 1,3-Dienes, such as butadiene, yield randomly distributed 1,2- and 1,4-copolymers. Oxygen pressure and olefin stmcture are important factors in these reactions for example, other products, eg, carbonyl compounds, epoxides, etc, can form at low oxygen pressures. Polymers possessing dialkyl peroxide moieties in the polymer backbone have also been prepared by base-catalyzed condensations of di(hydroxy-/ f2 -alkyl) peroxides with dibasic acid chlorides or bis(chloroformates) (110). 

This article will only discuss two particular kinds of photocycloaddition reactions, the photodimerization or cross-cycloaddition of two olefins to yield a cyclobutane derivative, and the photoreaction of an olefin with a carbonyl compound to give an oxetane, Eq. 1 and Eq. 2. The inportance of substituent effects in reactions of these types is pointed... 

Stabilized telluronium ylides such as dibutyltelluronium carbethoxy, phenacyl/ cyano- and carbamoylmethylide (easily prepared by the reaction of dibutyl teUurides with the appropriate substituted methyl hahdes, followed by treatment with a base), undergo Wittig-type olefmation reactions with a variety of carbonyl compounds, giving the expected olefins in satisfactory yields (method A). This behaviour is in sharp contrast to that of stabilized sulphonium yhdes, which are inert towards carbonyl compounds. 

The McMurry reaction (the reductive dimerization of carbonyl compounds giving olefins after treatment with the low-valent titanium reagents TiCla/Mg and TiCla/Zn in THF at 40°C) (CR891513) is a key step in the synthesis of photochromic cyclopentene derivatives. Later, it has been shown that TiCU, which is easier to handle than TiCls, can be used. The cyclization products are formed in 50-60% yields (98S1092,03EJO155). The advantages of this method are that the reactions can be scaled and inexpensive starting materials can be used. 

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