Hydrocarbons chiral

Transannular interactions lead to ring closures and reductions to adamantane compounds when dienes of the bicyclo[3.3.1]nonane family are treated with Brpnsted acids and triethylsilane. Compounds 48-51 form reaction mixtures containing various amounts of products 52-54 (R = OH, O2CCF3, Cl) under such conditions.243 The best yields of hydrocarbon 52 occur when the dienes are treated with a 25% excess of sulfuric acid and a 50% excess of triethylsilane in dichloromethane at 20°.243 The stereospecific nature of these transannular reductions is demonstrated by the observation that the enantiomeric purity of the chiral diene 55 is retained in the chiral hydrocarbon product 56 (Eq. 98).243 Dienes of... 

Initially, progress in this area was hampered by the lack of suitable analytical methods for chiral hydrocarbons. Early studies relied on optical rotation to determine enantiomeric excess (ee) values, but with the development of chiral gas chromatography (GC) and high-performance liquid chromatography (HPLC) columns, chromatographic methods have become more common. 

The chiral hydrocarbon germacrene D is a widely spread plant constituent and is considered to be an important intermediate in the biosynthesis of many sesquiterpenes. Schmidt et al. [19, 20] have shown that the plant Solidago canadensis generates both optical antipodes of this compound by enzymatic cyclisation of farnesyl diphosphate using two different enantiospecific synthases. As to be seen in Fig. 17.5, the enantiomeric ratio of germacrene D in Solidago canadensis can vary from individual to individual [21]. 

Alkanes and cycloalkanes. Obviously a variety of acyclic and cyclic hydrocarbon structures can be synthesized from the appropriate alkyl- or aryl-thiophenes (Scheme 46). The reaction is especially useful for the construction of macrocycles (Scheme 47). One of the most interesting applications of this reaction is in the synthesis of the chiral hydrocarbon butylethylmethylpropylmethane (210) (80JOC2754). The chiral acid (209) was the precursor, in which the thiophene was the potential n-butyl group. Raney nickel desulfurization, followed by standard manipulations to convert the acetic acid unit into an ethyl group, gave the hydrocarbon (210) (Scheme 48) this had [a]578 = -0.198°. It was established that... 

Hexahelicene is a chiral hydrocarbon with a helical structure. We found that (P)-hexahelicene with 0.13% ee, a lower ee than that induced by CPL [3,80], acts as a chiral initiator for asymmetric autocatalysis (Scheme 11). The reaction between pyrimidine-5-carbaldehyde 11 and i-Pr2Zn gave (S)-pyrimidyl alkanol 12 with 56% ee [83]. On the other hand, when (M)-hexahelicene with 0.54% ee was used instead of (P)-hexahelicene, (P)-12 with 62% ee was formed. As already described, these ee can be enhanced by further asymmetric autocatalysis. Thus, the chirality of CPL has been correlated with that of alkanol 12 with high ee by using hexahelicene as the chiral source of asymmetric auto catalysis. 

Chiral quaternary alkanes do not have any m-electrons or a heteroatom. Thus, the present chiral discrimination may involve the CH-7T interactions between the CH group of the chiral hydrocarbon and the m-electrons of the pyrimidine-5-carbaldehyde 11. This CH-jt interaction [109] maybe used to discriminate between the Re and Si enantiofaces of aldehyde 11, because the... 

Chiral Hydrocarbons Act as Chiral Initiators (S-Indudng Enantiomer)... 

In addition, saturated tertiary hydrocarbons [108] also act as a chiral source of asymmetric autocatalysis to give the pyrimidyl alkanol, with the absolute configurations corresponding to that of the chiral alkanes (Scheme 21). The correlation between the absolute configuration of the hydrocarbon and that of the obtained alkanol is reproducible. Therefore, the asymmetric autocatalysis is sufficiently applicable as a chiral sensor for saturated tertiary hydrocarbons. Various chiral hydrocarbons with zr-electrons such as 1,1 -binaphthyls [110], helicenes [82], olefins [83], allenes [111], and [2.2]paracy-clophanes [112,113] serve as chiral initiators in this asymmetric autocatalysis. 

Power TD, ShoU DS (1999) Enantiospecific adsorption of chiral hydrocarbons on natiuaUy chiral Pt and Cu surfaces. J Vac Sd Technol A 17 1700... 

Since the previous review, new work has been carried out which has enlarged the synthetic scope of this reaction, including the use of new dienes (e.g. of favorable rigid structures) or new dienophiles (such as phosphaalkynes), as well as the use of high pressure and, more importantly, catalysis by low-valent transition metal complexes which permits the use of non-functionalized alkenes or alkynes, thus opening a new route to polycyclic and chiral hydrocarbons. 

Dihalocarbene adducts from bicyclic and polycyclic exomethylene hydrocarbons upon de-halogenation with alkyllithiums give the corresponding exocyclic allenes. Many of these allenes are chiral by virtue of their chiral hydrocarbon precursors (/ -pinene, camphene, etc.). Examples are the dehalogenation of 60, ° 62, 64, 66, 68, and 70. ... 

Clathrates of [tri-O-thymotide (TOT), brucine, sparteine, 2,2 -dihydroxy-1,1 -binaphthyl-diol] Alkanes, unbranched chiral hydrocarbons, acids and esters bearing small substituents, halogenated hydrocarbons, sulfoxides, phosphine oxides, phosphinates, piperidines [59-64]... 

Preparation of enantiomerically active hydrocarbons is difficult and only a few examples of the preparation of chiral hydrocarbons have been reported. For example, chiral 3-phenylcyclohexene has been derived from tartaric acid through eight synthetic steps. Enantiomeric separation by host-guest complexation with a chiral host is more fruitful for the preparation of chiral hydrocarbons. For example, when a solution of fR,Rh( )-t ws-4,5-bis(hydroxydiphenylmethyl)-l,4-dioxaspiro[4.4]-nonane (lb) [2] (3 g, 6.1 mmol) and rac-3-methylcyclohexene (2a) (0.58 g, 6.1 mmol) in ether (15 ml) was kept at room temperature for 12 h, a 2 1 inclusion complex of lb and 2a (2.5 g, 75%) was obtained as colorless prisms in the yield indicated. The crystals were purified by recrystallization from ether to give the inclusion complex (2.4 g, 71%), which upon heating in vacuo gave (-)-2a of 75% ee by distillation (0.19 g, 71%) [3]. By the same inclusion complexation, (-i-)-4-methyl- (2b) (33% ee, 55%), (-)-4-vinylcyclohexene (2c) (28% ee, 73%), (-)-bicyclo[4.3]-nonane-2,5-diene... 

Lesot E, Sarfati M, and Courtieu J (2003) Natural abundance deuterium NMR spectroscopy in polypeptide liquid crystals as a new and incisive means for the enatiodifferentiation of chiral hydrocarbons. Chemistry -A European Journal 9 1724—1745. 

Wynberg has reported three syntheses of spiro[3,3]hepta-l,5-diene (294), which are summarized in Scheme 23. This chiral hydrocarbon has been resolved via diastere-... 

Many hydrocarbons are by-products of the petroleum industry and some of them are chiral in nature. The most important chiral hydrocarbons are halogenated, polyalkane and so on. These hydrocarbons are also used as precursors for many synthetic formulations and products, in which chiral products are produced during the synthesis processes. The different oilfields have been produced from various materials at different times, and hence different ratios of stereoisomers can be found in samples from adjacent fields. Briefly, chirality is of considerable importance in the petrochemical industry. 

SEPARATION PROCESSES IN GAS-LIQUID CHROMATOGRAPHY BASED ON FORMATION OF a-CYCLODEXTRIN - CHIRAL HYDROCARBONS INCLUSION COMPLEXES... 

A simple and very convenient method for the determination of enantiomeric purity of chiral hydrocarbons, recently developed at this Laboratory, is another interesting application of chromatographic separation of enantiomers via inclusion complexes with a-CD. 

Koscieleki, T., D. Sybilska and J. Jurczak - Separation processes in gas liquid chromatography based on the formation of alpha cyclodextrin - chiral hydrocarbon inclusion complexes 69... 

Optically active porphyrin derivatives have drawn the attention of biologists relevance and industrialist due to its wide range of applications in the fields of nonlinear optics and chiral catalysis [74-80]. Subsequently, a number of chiral amino acids and chiral hydrocarbons based porphyrin-chiral substituents molecules have been synthesized. It is interesting to note that the presence of stereocenters onto the periphery of porphyrin molecule provides just a possibility for fabrication of helical supramolecular structures and optically active porphyrin molecules. 

Very recently the crystal structure of the other semibuckminsterfullerene 20 was determined by X-ray study in the Petrukhina laboratory [25]. Unfortunately the random distribution of both enantiomers of the chiral hydrocarbon precluded the precise determination of the molecular geometry, but allowed observation of the packing patterns in two different polymorphs that revealed an endo-exo stacking of the bowls of 20 in one of them [25]. 

V. Schurig and D. Kreidler, Gas-Chromatographic Enantioseparation of Unfunctionalized Chiral Hydrocarbons An Overview, in Chiral Separation Methods and Protocols, ed. K. E. Scriba, Methods in Molecular Biology, Springer, New York, NY, United States, 2013, vol. 970, p. 45. 

Chiral hydrocarbon with a molecular ion at miz = 82 Molecular formula CeHio... 

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