Some Stability and Stereochemical Considerations of Simple Bicyclo[4.2.0]octanols

2005 ◽  
Vol 58 (5) ◽  
pp. 354 ◽  
Author(s):  
Wendy A. Loughlin ◽  
Catherine C. Rowen ◽  
Michelle A. McCleary
Keyword(s):  
Hydrogen Bonding ◽  
Hydrochloric Acid ◽  
Reaction Temperature ◽  
Ring Opening ◽  
Unexpected Result ◽  
Lithium Diisopropylamide ◽  
Aqueous Hydrochloric Acid ◽  
Ring Open ◽  
Short Times

Bicyclooctanols 3 and 4 were formed with control of the stereochemistry at C8 by using an aluminium enolate of cyclohexanone in 1,2-dimethoxyethane. Bicyclooctanols 1 and 3 were stable towards aqueous hydrochloric acid for short times (< 3.5 h), and ring open to a diastereomeric mix of monoalkylated 5 under protic or aprotic conditions in the presence of base (NaOH or lithium diisopropylamide). The rate of ring opening appears to be dependent on reaction temperature. Bicyclooctanols 1, 3, and 4 displayed remarkable stability when heated at reflux in benzene, whereas use of ethanol prompted stereoselective ring opening of 1 and 3 to give individual diastereomers of monoalkylated 5 and ring opening of 4 to give a 50 : 50 mix of diastereomers of 5. This unexpected result was attributed to the stereochemistry of the bicyclooctanol and placement of hydrogen-bonding sites.

Ring-Opening Polymerization of Lactide Using Aluminum Salen-Type Initiators

2014 ◽  
Vol 915-916 ◽  
pp. 713-716
Author(s):  
Qing Zhang ◽  
Jing Tian ◽  
Zhi Qi Cao ◽  
Ru Xia Xu ◽  
Zhen Zhen Sun ◽  
...  
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Infrared Spectroscopy ◽  
Reaction Time ◽  
Magnetic Resonance ◽  
Schiff Bases ◽  
Reaction Temperature ◽  
Ring Opening ◽  
Ring Opening Polymerization ◽  
Resonance Spectroscopy ◽  
Aluminum Complex

In this investigation, Schiff bases aluminum complex was synthesized and used as the initiator in the polymerization of D,L-lactide. The aluminum complex was characterized by infrared spectroscopy (IR), and nuclear magnetic resonance spectroscopy (NMR). The influences of different factors, including reaction time, reaction temperature, and the ratio of D, L-lactide/Al3+ on the synthesis of polylactide were described. The results showed that Schiff bases aluminum complex could be successfully applied in the ring opening polymerization. The optimum condition of the ring opening polymerization of D,L-lactide, which included D,L-lactide/Al3+ (mol/mol) ratio of 250, reaction temperature of 120 °C, and reaction time of 16 hours.

Stereoselective deprotonation of tropinone and reactions of tropinone lithium enolate

1992 ◽  
Vol 70 (10) ◽  
pp. 2618-2626 ◽  
Author(s):  
Marek Majewski ◽  
Guo-Zhu Zheng
Keyword(s):  
Acetic Acid ◽  
Ring Opening ◽  
Aldol Reaction ◽  
Ethyl Chloroformate ◽  
Lithium Diisopropylamide ◽  
Silver Acetate ◽  
Lithium Amides ◽  
Lithium Enolate ◽  
The Absolute ◽  
Absolute Stereochemistry

Tropinone (6) was deprotonated with lithium diisopropylamide and with chiral lithium amides (18–24) and the resulting enolates (two enantiomers) were treated with electrophiles. The aldol reaction with benzaldehyde and deuteration were both diastereoselective. The former yielded only one isomer (exo, anti) of the aldol 8a; the latter proceeded from the exo face. This selectivity permitted us to probe the deprotonation of tropinone with lithium amides; it was concluded that the reaction involves predominantly the exo axial protons. The reaction of tropinone enolate with ethyl chloroformate led, via a ring opening, to the cycloheptenone derivative 9. The reaction with methyl cyanoformate yielded, in the presence of silver acetate and acetic acid, the β-ketoester 8b; however, in the absence of these additives, and especially when 12-crown-4 was added to the enolate, a ring opening leading to the pyrrolidine derivative 10 occurred instead. Deprotonation of tropinone with chiral lithium amides proceeded with modest enantioselectivity. A synthesis of non-racemic anhydroecgonine via this strategy allowed establishing the absolute stereochemistry of deprotonation.

A 35Cl magnetic resonance study of chloride exchange on indium(III) and thallium(III) in aqueous hydrochloric acid solution

1975 ◽  
Vol 28 (9) ◽  
pp. 1901 ◽  
Author(s):  
SF Lincoln ◽  
AC Sandercock ◽  
DR Stranks
Keyword(s):  
Exchange Rate ◽  
Magnetic Resonance ◽  
Hydrochloric Acid ◽  
Acid Solution ◽  
Hydrochloric Acid Solution ◽  
Magnetic Resonance Study ◽  
Aqueous Hydrochloric Acid ◽  
Chloride Exchange ◽  
Lower Limits ◽  
Aqueous Hydrochloric Acid Solution

The parameters describing chloride exchange on indium(III), determined by 35Cl N.M.R., are: k(298 K)= (8.8�0+4) x 106 s-1, ΔH? = 45.7�2.3 kJ mol-1 and ΔS? = 42�8 J mol-1 K-1; and k(298 K)= (2.0�0.1)x106 s-1, ΔH? = 37.7�1.9 kJ mol-1, and ΔS? = 3�6 J mol-1 K-1 in 10.95M and 7.00M aqueous hydrochloric acid respectively, calculated from the observed exchange rate kex4[InCl4(H2O)2-].��� For thallium(III) lower limits of kex(219 K) = 1.6 x 106 s-1 and 1.3 x 106 s-1 were obtained in 10.95M and 7.00M aqueous hydrochloric acid, respectively, where [TlCl6]3- is assumed to be the exchanging species.

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