Crotyl chlorides

The dienone 858 is synthesized by coupling of the alkenyl copper reagent 856 with crotyl chloride (857) in the presence or absence of ZnCl2[731], Tetrabutyllead (859) reacts with benzoyl chloride to afford butyl phenyl ketone[732]. 

It was suggested that this change in product distribution was due to the existence of an equilibrium between two types of complex, viz., a cr-butenyl-pentacyanocobaltate(III) and a 7r-butenyltetracyanocobaltate(III) 107, 109). However, further study of the kinetics and product distribution suggested the presence of two o-bonded complexes, viz., cr-but-l-en-3-yl and a-but-2-en-l-yl 24a). Direct evidence for the existence of a cyanide-dependent equilibrium between the a- and rr-bonded organocyanide complexes has been obtained from NMR studies of the complex prepared by the reaction of allyl halides with Co—H 109) (see also Section V,C). Both butadiene and crotyl chloride react with Co—H to give the same... 

The reaction of crotyl bromide with ethyl diazoacetate once again reveals distinct differences between rhodium and copper catalysis. Whereas with copper catalysts, the products 125 and 126, expected from a [2,3] and a [1,2] rearrangement of an intermediary halonium ylide, are obtained by analogy with the crotyl chloride reaction 152a), the latter product is absent in the rhodium-catalyzed reaction at or below room temperature. Only when the temperature is raised to ca. 40 °C, 126 is found as well, together with a substantial amount of bromoacetate 128. It was assured that only a minor part of 126 arose from [2,3] rearrangement of an ylide derived from 3-bromo-l-butene which is in equilibrium with the isomeric crotyl bromide at 40 °C. 

Following the reactions in Scheme 4, the olefin 13 would have to be generated before the formation of the 7r-crotyl species 2. Because the amount of the catalyst present is usually small as compared to the amount of product formed (1000 moles of product/mole catalyst), the quantity of 13 produced will not be significant and should be readily separable from the desired product. In the special case when crotyl chloride is used as the activator, hexadiene can be produced during the very first cycle of reaction, i.e., 13 = 1,4-hexadiene. Among the organic halides, the chloride derivatives are the most effective activators. Bromides are somewhat effective, while fluorides and iodide are rather ineffective (77). 

Crotononitrile, b482 trans-Crotonyl alcohol, c311 Crotyl alcohols, b486, b487 Crotyl bromide, b276 Crotyl chloride, c79... 

This a-alkylation cuprate displacement sequence is also applicable to anions of mcthallyl and crotyl chloride and is a promising route to more complex systems. 

This book makes a substantial break with tradition in the matter of organic nomenclature. It was difficult to decide to do this because changes in this area are very hard to achieve, perhaps for the reason that they threaten the viability of what already is published and, indeed, even our customary forms of verbal communication. One of the authors remembers vividly the protests of his thesis supervisor to the idea of acquiescing to the admonition of a manuscript reviewer who felt that crotyl chloride and methylvinylcarbinyl chloride represented just too much of a mixing of nomenclature systems for isomeric compounds. But we ve used those names in nineteen earlier papers Nonetheless, organic chemists and organic chemistry will surely be better off to name these same compounds systematically as l-chloro-2-butene and 3-chloro-l-butene. 

Crotyltri-n-butyltin, CH3CH=CHCH2Sn(C4H9-n)3 (1). (n-Bu)3SnLi reacts with (E)-or (Z)-crotyl chloride in THF at — 20 to form (E)- or (Z)-crotyltri-n-butyltin with complete retention of the stereochemistry of the double bond. 

The substitution pattern in the product obtained through this sequence was in agreement with the proposed mechanism (Table 3.7). For example, crotyl chloride gave the 2-chloro-3-methyl hex-4-enoates (entries 3 and 4), and propargyl bromides gave the allenic products (e.g., entries 7 and 8). Yields were usually better with the more substituted tert -butyl diazoacetate. 

The coupling occurred at the less-hindered terminal carbon giving thermally stable ( )-allyl boronates. Thus, the (.E)- and (Z)-crotyl chloride, and 3-chloro-l-butene, all afforded an (A)-crotyl boronate. The reaction with benzyl halides gave benzyl boronates.333... 

Experimental. Butenylmagnesium chloride was prepared from crotyl chloride and magnesium chips in ether. Decomposition reactions of butenylmagnesium chloride were carried out at room temperature using H20 and D20. Butenes were condensed at — 20 °C. and analyzed on a FB-4 Shandon ionization chromatograph. 

Bis(7r-crotylpalladium chloride) was prepared by the reaction of palladium chloride solution in 50% acetic acid with crotyl chloride at +30°C. (19). 

Polymerization was carried out in benzene in the presence of bis-(7r-allylnickel halides). The latter were prepared from nickel carbonyl and allyl halide (allyl bromide, crotyl chloride, bromide, or iodide etc.). The results of the polymerization runs are reported in Table I. The data indicate that all of the bis(7r-allylnickel halides) initiate by themselves the stereospecific butadiene polymerization yielding a polymer with 97-98% 1,4-units. The cis-l,4/trans-l,4 ratio depends on the halide in the dimeric r-allylnickel halide but not on the nature of allylic ligand. The case of bis(7r-crotylnickel halides) shows the effect of halide on microstructure, for whereas (C4H7NiCl)2 initiates cis- 1,4-polybutadiene formation, trans-1,4 polymers are produced by (C4H7NiI)2. The reactivity increase in the series Cl < Br < I. 

One case where C—C bonds are exceptionally effective in hyperconjugation is in the stabilisation provided by a cyclopropyl substituent to an empty p orbital. The cyclopropylmethyl cation is actually better stabilised than an allyl cation, as judged by the more rapid ionisation of cyclopropylmethyl chloride 2.19 than of crotyl chloride 2.20. In this case, hyperconjugation appears, unusually, to be better than n conjugation. 

An additional element of complication in preparing the allyl ethers utilizing the salts of hydroxypyridines lies in the intervention of SN2 displacements. Thus the sodium salt of 2-pyridone on treatment with crotyl chloride or with 3-chloro-1 -butene afforded the same compound, viz., l-crotyl-2-pyridone5 [Eq. (1)]. 

Allylic chlorides, e.g., allyl, methallyl, and crotyl chlorides, are very reactive and are employed in the synthesis of unsaturaled ethers Besides the usual coupling of the sodium alcoholate and halide in alcohol solutions other conditions have been described, including reaction of the alcohol and unsaturated halide in the presence of potassium carbonate or sodium hydroxide in acetone or water. The combination of anhydrous potassium carbonate and acetone is widely used in the preparation of allyl aryl ethers the reaction is aided by the addition of finely powdered potassium iodide. ... 

If the cyclobutene-vinylketene equilibrium is established in the presence of a 1,3-diene such as cy-clopentadiene, cyclohexadiene or ( )-l,3-pentadiene, the ketene is trapped via a [4 + 2] cycloaddition reaction to furnish a 2,3-divinylcyclobutanone (127). When such reactions are carried out above 120 C a further 3,3-sigmatropic rearrangement takes place to yield cyclooctadienones (128) in overall yields ranging from 30-90%. The intermediate divinylcyclobutanes can also be obtain by dehydrohalogenation of crotyl chloride in the presence of the dienes. ... 

A variety of alkynes follow this reaction sequence in reactions with allyl and crotyl chlorides, as well as with methyl 4-bromocrotonate. All examples proceed with total regioselectivity with respect to carb-... 

With allylic chloroformates, substitution may also occur via a six-centred transition state. Thus Oliver and Young have demonstrated that for the pure liquids or in a variety of solvents both a-methylallyl and y-methylallyl (crotyl) chloroformate thermally decompose to yield a mixture of a-methylallyl chloride and y-methylallyl (crotyl) chlorides. At 75 °C the ratio of a-methylallyl chloride to y-methylallyl chloride produced from pure a-methylallyl chloroformate is 47 53 the corresponding ratio from y-methylallyl chloroformate is 63 37. 

Other alkyl chlorides tested are crotyl chloride (99) and n- and f rt-butyl chlorides (100) catalyzed with pyridine. Again, the ASE is only temporary and the liberated HCl causes severe degradation. 

Crotyl chloride or 3-chloro-l-butene reacts in aqueous media to give T7-allylic complexes and a hydroxyl carbonyl compound, which reacts again to give a dicarbonyl 151) ... 

The reaction of crotyl chloride with TMSCI under Barbier conditions yields the same ratio of products as the reaction of the preformed crotyl Grignard reagent with TMSCI in ether [Eq. (64) 130]. 

Wilson [7] invoked a common ion-pair intermediate (an 8Nl-like mechanism) to justify the identical product mixture so obtained. Czerneki [8] described the same type of intermediate in the reaction of cis- and rmns-crotyl chloride with organomagnesium reagents. Ireland [9] showed that for a tetrasubstituted double bond, the sole 8n2 product 6 was formed on reaction with proparglymagnesium bromide [Eq. (2)]. 

Tri-n-butylcrotyltin (1). (Z)- or (E)-Crotyl chloride reacts with tri-n-butyltinlithium to form (Z)- or (E> 1 with retention of the geometry of the double bond1 ... 

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