1. A method for checking ice formation on an aircraft in flight, the method comprising:
estimating in real time a quantity of ice forming on at least one zone of the aircraft based on flight conditions; and
comparing the estimated quantity of ice to a plurality of predetermined quantities of ice thresholds,
wherein the plurality of predetermined quantities of ice thresholds respectively correspond to distinct flight phases of the aircraft.
2. The method according to claim 1, wherein the estimation in real time of the quantity of ice is based on a distance traveled by the aircraft and on a quantity of liquid water available to turn into ice on the aircraft.
3. The method according to claim 1, wherein the estimation in real time of the quantity of ice uses an average rate of ice accretion corresponding to the estimated quantity of ice, and the comparison of the estimated quantity of ice to the plurality of predetermined quantities of ice thresholds is performed based on the estimated rate of ice accretion and at least one predetermined rate of ice accretion.
4. The method according to claim 1, further comprising estimating an amount of time remaining for the aircraft to fly under freezing conditions until reaching a predetermined quantity of ice.
5. The method according to claim 1, wherein one of the predetermined quantities of ice thresholds is less than a maximal quantity of ice set at a time of a process for certification of the aircraft in freezing conditions.
6. The method according to claim 1, comprising, based on a result of the comparison, activating at least one of a deicing device on board the aircraft and an alarm system that transmits at least one of a visual and an auditory alarm message.
7. The method according to claim 1, further comprising estimating a time remaining until the estimated quantity of ice reaches one or more of the predetermined quantities of ice thresholds.
8. The method according to claim 1, further comprising estimating a time remaining until the estimated quantity of ice reaches a predetermined quantity of ice, the predetermined quantity of ice being a maximal quantity of ice set according to an aircraft certification process of the aircraft for flying in freezing conditions.
9. The method according to claim 1,
wherein the plurality of predetermined quantities of ice thresholds include first, second, and third quantities of ice thresholds, and
the method further comprising activating an alarm based on a result of the comparison indicating the estimated quantity of ice has reached any of the first threshold, the second threshold, and the third threshold,
wherein the first threshold represents an onset of freezing conditions and the third threshold represents a maximal quantity of ice set according to an aircraft certification process of the aircraft for freezing conditions.
10. The method according to claim 1, wherein the estimation in real time of the quantity of ice includes:
obtaining a speed of the aircraft, and
obtaining a value for a quantity of liquid water available to turn into ice on the aircraft.
11. The method according to claim 10, wherein the obtaining the value for the quantity of liquid water includes measurement of a quantity of liquid water encountered by the aircraft during flight.
12. The method according to claim 10, wherein the value for the quantity of water obtained is a predetermined value determined prior to the flight.
13. A system to check ice formation on an aircraft in flight, the system comprising:
a processor including:
an ice quantity estimation unit to estimate in real time a quantity of ice forming on at least one zone of the aircraft to based on flight conditions; and
a comparing unit to compare the estimated quantity of ice to a plurality of predetermined quantities of ice thresholds,
wherein the plurality of predetermined quantities of ice thresholds respectively correspond to distinct flight phases of the aircraft.
14. An aircraft comprising the system according to claim 13.
15. The system according to claim 13, wherein the processor further includes an alarm generation unit to generate an alarm for a manual deicing operation based on an output of the comparing unit indicating that the estimated quantity of ice meets or exceeds one of the predetermined quantities of ice thresholds.
16. The system according to claim 13, wherein the processor further includes an automatic deicing unit that is activated to deice the at least one zone of the aircraft responsive to an output of the comparing unit indicating the estimated quantity of ice meets or exceeds one of the predetermined quantities of ice thresholds below a maximal quantity of ice.
17. The system according to claim 13, wherein the processor further includes a time estimating unit to estimate an amount of time remaining until the estimated quantity of ice reaches one or more of the predetermined quantities of ice thresholds.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
We claim:
1. A process for preparing 6-hydroxy-3,4-dihydroquinolinone by cyclization of N-(4-methoxyphenyl)-3-chloropropionamide comprising the steps of:
a) contacting an equivalent of N-(4-methoxyphenyl)-3-chloropropionamide with about 3 to about 5 equivalents of a Lewis acid catalyst in a diluent selected from the group consisting of dimethyl sulfoxide, N,N-disubstituted amides and amines having a boiling point of 150 C. or above, the diluent being present in an amount of from about 1 to about 1.3 equivalents with respect to the N-(4-methoxyphenyl)-3-chloropropionamide, at an elevated temperature of from about 150 C. to about 220 C. for a period of time sufficient to cause substantially all of the N-(4-methoxyphenyl)-3-chloropropionamide to cyclize and demethylate resulting in the formation of a Lewis acid salt of 6-hydroxy-3,4-dihydroquinolinone, and thereafter,
b) decomposing the Lewis acid salt of 6-hydroxy-3,4-dihydroquinolinone, and
c) isolating 6-hydroxy-3,4-dihydroquinolinone.
2. The process of claim 1 wherein the Lewis acid is selected from the group consisting of AlCl3, AlBr3, FeCl3, FeBr3, SbF5, TiCl4, SnCl4 and BF3.
3. The process of claim 2 wherein the Lewis acid is AlCl3.
4. The process of claim 3 wherein the N-(4-methoxyphenyl)-3-chloropropionamide is contacted with about 4 equivalents of AlCl3.
5. The process of claim 1 wherein the time sufficient to cause substantially all of the N-(4-methoxyphenyl)-3-chloropropionamide to cyclize is three hours or less.
6. The process of claim 1 wherein the N-(4-methoxyphenyl)-3-chloropropionamide and Lewis acid are contacted at an elevated temperature of from about 150 C. to about 160 C.
7. The process of claim 1 and thereafter converting the 6-hydroxy-3,4-dihydroquinolinone to 6-4-(1-cyclohexyl-1H-tetrazol-5-yl)butoxy-3,4-dihydro-2(1H)-quinolinone or a pharmaceutically acceptable salt thereof.
8. The process of claim 7 wherein the conversion of 6-hydroxy-3,4-dihydroquinolinone to 6-4-(1-cyclohexyl-1H-tetrazol-5-yl)butoxy-3,4-dihydro-2(1H)-quinolinone or a pharmaceutically acceptable salt thereof is by reaction of 6-hydroxy-3,4-dihydroquinolinone with a 1-cyclohexyl-5-(4-halobutyl)-tetrazole in the presence of an organic or inorganic base.
9. 6-Hydroxy-3,4-dihydroquinolinone prepared by the process of claim 1.
10. A process for preparing 6-hydroxy-3,4-dihydroquinolinone by cyclization of N-(4-methoxyphenyl)-3-chloropropionamide comprising the steps of:
a) contacting an equivalent of N-(4-methoxyphenyl)-3-chloropropionamide with about 3 to about 5 equivalents of a Lewis acid catalyst in a reaction medium consisting essentially of a diluent selected from the group consisting of dimethyl sulfoxide, N,N-disubstituted amides and amines having a boiling point of 150 C. or above, the diluent being present in an amount of from about 1 to about 1.3 equivalents with respect to the N-(4-methoxyphenyl)-3-chloropropionamide, at an elevated temperature of from about 150 C. to about 220 C. for a period of time sufficient to cause substantially all of the N-(4-methoxyphenyl)-3-chloropropionamide to cyclize and demethylate resulting in the formation of a Lewis acid salt of 6-hydroxy-3,4-dihydroquinolinone, and thereafter,
b) decomposing the Lewis acid salt of 6-hydroxy-3,4-dihydroquinolinone, and
c) isolating 6-hydroxy-3,4-dihydroquinolinone.
11. 6-Hydroxy-3,4-dihydroquinolinone prepared by the process of claim 10.
12. A process for preparing N-(4-methoxyphenyl)-3-chloropropionamide comprising the steps of adding p-anisidine and from about 1 to 1.2 equivalents of sodium bicarbonate with respect to the p-anisidine to toluene to form a suspension of sodium bicarbonate in a p-anisidine solution, slowly adding from about 0.9 to about 1.1 equivalents of 3-chloropropionyl chloride to the suspension, maintaining the temperature of the suspension at from about 25 C. to about 111 C. for a period of time sufficient to cause substantially all of the p-anisidine to be converted to N-(4-methoxyphenyl)-3-chloropropionamide, quenching the mixture with aqueous mineral acid, wherein quenching causes precipitation of solid, and isolating the solid from the quenched mixture, further wherein after washing with water and toluene, followed by drying to a constant weight, the solid that is obtained is N-(4-methoxyphenyl)-3-chloropropionamide in greater than 98% purity.
13. N-(4-methoxyphenyl)-3-chloropropionamide made by the process of claim 12.
14. A process for preparing N-(4-methoxyphenyl)-3-chloropropionamide comprising the steps of adding p-anisidine and from about 1 to 1.2 equivalents of triethylamine with respect to the p-anisidine to methyl ethyl ketone, slowly adding from about 0.9 to about 1.1 equivalents of 3-chloropropionyl chloride, heating the resulting mixture to reflux temperature, precipitating a solid from the reaction mixture by cooling, and isolating the solid from the mixture, wherein after washing with water and drying to constant weight the solid that is obtained is N-(4-methoxyphenyl)-3-chloropropionamide in greater than 98% purity.
15. N-(4-methoxyphenyl)-3-chloropropionamide made by the process of claim 14.
16. A process for preparing N-(4-methoxyphenyl)-3-chloropropionamide comprising the steps of dissolving p-anisidine in dichloromethane to form a N-(4-methoxyphenyl)-3-chloropropionamide solution and adding from about 0.9 to about 1.1 equivalents of 3-chloropropionyl chloride and from about 0.9 to about 1.1 equivalents sodium hydroxide at a temperature of 0 C. or less and in a concerted manner that maintains approximately neutral pH in the (4-methoxyphenyl)-3-chloropropionamide solution, precipitating a solid from the dichlormethane phase of the resulting two phase mixture and separating the solid from the dichloromethane, wherein after washing with water and drying to constant weight the solid that is obtained is N-(4-methoxyphenyl)-3-chloropropionamide in greater than 98% purity.
17. N-(4-methoxyphenyl)-3-chloropropionamide made by the process of claim 16.
18. A process for preparing N-(4-methoxyphenyl)-3-chloropropionamide comprising the steps of dissolving p-anisidine in N,N-dimethylformamide and adding from about 0.9 to about 1.1 equivalents 3-chloropropionyl chloride with respect to the p-anisidine to the solution for a time sufficient to form N-(4-methoxyphenyl)-3-chloropropionamide, adding water to the mixture, whereupon addition of the water causes a solid to precipitate from the mixture, isolating the solid from the mixture, wherein after washing with water and drying to a constant weight the solid is N-(4-methoxyphenyl)-3-chloropropionamide in greater than 98% purity.
19. N-(4-methoxyphenyl)-3-chloropropionamide made by the process of claim 18.