Chromium chloride—Lithium iodide

Oxygen-substituted allylchromium reagents are conveniently generated from vinyloxi-ranes by chromium(II) chloride in the presence of lithium iodide and aldehydes with high anti diastereoselectivity14. qh oh... 

ALLENES Alkyllithium reagents. Chromium(HI) chloride-Lithium aluminum hydride. Formaldehyde. N,N-Mcthylphcnylamino(tri-n-butylphos-phonium) iodide. Tricthyl orthoaeetate. Trimethylsilylm ethyEmagncsium chloride. 

Catalysed aerobic epoxidation of the styrene-cobalt complex, followed by the addition of trimethylsilyl isothiocyanate, yields 4-phenyloxazolidine-2-thione 123 <96TL7315>. The 4-substituted 2-oxazolidinone 124 undergoes a "chromium Reformatsky" reaction with aldehydes RCHO (R = i-Pr or Ph) in the presence of chromium(ll) chloride and lithium iodide to give mainly the unusual anti-aldol products 125 in excellent dia,stereomeric excess and yield <97TL4,387>. 

Related Reagents. Lithium Aluminum Hydride-(2,2 -Bipy-ridyl)(l,5-cyclooctadiene)nickel Lithium Aluminum Hydride-Bis(cyclopentadienyl)nickel Lithium Aluminum Hydride-Boron Trifluoride Etherate Lithium Aluminum Hydride-Cerium(III) Chloride Lithium Aluminum Hydride-2,2 -Dihydroxy-l, E-binaphthyl Lithium Aluminum Hydride-Chromium(III) Chloride Lithium Aluminum Hydride-Cobalt(II) Chloride Lithium Aluminum Hydride-Copper(I) Iodide Lithium Aluminum Hydride-Diphosphoms Tetraiodide Lithium Aluminum Hydride-Nickel(II) Chloride Lithium Aluminum Hydride-Titanium(IV) Chloride Titanium(III) Chloride-Lithium Aluminum Hydride. 

A dichromium derivative has been prepared from pinacol (dichloromethyl)-boronate (163), anhydrous chromous chloride, and lithium iodide in THF at 25 °C [90]. With various aldehydes, RCHO, this reagent adds to the carbonyl carbon to form trans-l-alkenylboronic esters, RCH=CH-B(02C2Me4). For most examples yields were 84-91%, E Z ratios >95 5. This reaction was used recently to convert aldehyde 162 into alkenylboronic ester 164, an intermediate used for a Suzuki-Miyaura coupling in the asymmetric total synthesis of quinine and quinidine (Scheme 8.39) [91]. In the modified procedure, the chromium reagent was generated from 163 in the presence of the aldehyde substrate. 

Various other reagents can be used for this reductive debromination. 1,2-Dipropylcyclopropane was prepared from 4,6-dibromononane using chromium(II) perchlorate in dimethylformami-de/water (yield 93%), lithium amalgam in tetrahydrofuran (75%), lithium biphenylide in te-trahydrofuran (78%), potassium-sodium alloy in tetrahydrofuran (68%), zinc dust and zinc(II) chloride in propan-2-ol/water (95%) and alkyllithiums in tetrahydrofuran (BuLi 16%, i-BuLi 18%, t-BuLi 47%). Ring closure of 1,3-dibromobutane to methylcyclopropane was achieved by treatment with zero-valent copper, which was obtained from reaction of lithium naphthalen-ide and copper(I) iodide/tributylphosphane in tetrahydrofuran (yield 91%) ... 

Treatment of (31) with crotyl chloride-potassium carbonate in DMF afforded (33), which was converted into (34) by heating in a sealed tube. Methylation of the phenol (34) with methyl iodide-potassium carbonate gave (35). Osmic acid-sodium periodate oxidation produced the keto-aldehyde (36). Acetalization by standard methods gave the diacetal (37). Reduction of (37) with lithium in liquid ammonia and subsequent toluene-p-sulphonic acid work-up afforded (38) in a yield of 50 %. A vinylogous aldol condensation was effected with methan-olic potassium hydroxide. The resulting mixture was oxidized with chromium... 

Chromic anhydride-pyridine, 70 Chromium hexacarbonyl, 71 Chromones, 423 Chromous chloride, 73 Chrysanthemic acid, 49, 50, 207-208 Chrysanthemic esters, 183-184 Cinnamic esters, 362 CitroneUol, 5, 308, 309 Claisen rearrangement, 2, 372 Clemmensen reduction, 426 Cocaine, 384 Codeine, 236, 347, 348 Conjugate addition, 86, 102, 119-120, 133, 226-227, 253, 353, 400 Cope rearrangement, 66, 397 Copper, 73-74 Copper(I) acetate, 80 Copper(II) acetate, 39, 117, 126, 186 Copper(I) bromide-Lithium trimethoxy-aluminum hydride, 80 Copper(I) bromide, 79-80 Copper(I) chloride, 50, 80-81 Copper(II) chloride, 126, 79 Copper(l) cyanoacetate, 74 Copper halide nitrosyls, 73 CopperO) iodide, 81-82 Copper(I) methyltrialkylborates, 4,75 CopperGD perchlorate. 79 COpper(I) phenylacetylide, 237 Copper(II) sulfate, 117 CopperO) trifluoiomethanesulfonate, 75-76... 

Write a molecular equation for the precipitation reaction that occurs (if any) when each pair of solutions is mixed. If no reaction occurs, write NO REACTION. (a) sodium carbonate and lead(II) nitrate (b) potassium sulfate and lead(II) acetate (c) copper(II) nitrate and barium sulfide (d) calcium nitrate and sodium iodide 66. Write a molecular equation for the precipitation reaction that occurs (if any) when each pair of solutions is mixed. If no reaction occurs, write NO REACTION. (a) potassium chloride and lead(II) acetate (b) lithium sulfate and strontium chloride (c) potassium bromide and calcium sulfide (d) chromium(III) nitrate and potassium phosphate... 

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