On August 20, 2017, about 1700 eastern daylight time, a Cessna 180, N1585C, was substantially damaged while taxiing for takeoff at Parlin Field Airport (2B3), Newport, New Hampshire. The commercial pilot was not injured. The airplane was being operated under the provisions of Title 14 Code of Federal Regulations Part 91 as a personal flight. Visual meteorological conditions prevailed at the time and no flight plan was filed for the flight that was originating at the time of the accident, and was destined for Rutland-Southern Vermont Regional Airport (RUT), Rutland, Vermont.The pilot stated that he performed a preflight inspection of the airplane that included an inspection of the wheel assemblies and noted no fluid was on the ground. After engine start, he performed an engine run-up, and reported no issues with the brakes. He then back-taxied to the approach end of runway 36. While taxiing, he noted the left brake pedal did not line-up exactly with the right brake pedal; however, he noted that the difference in brake pedal position had been that way for a while. He continued to taxi, steering with the tailwheel. When near the approach end of the runway while starting to slow; the left brake was normal, but the right brake pedal traveled completely to the floor. In an effort to avoid trees off the side of the runway, he intentionally ground-looped the airplane. He believed the airplane ground-looped twice, and on the second turn, he added power to get some rudder authority which only exacerbated the turn. The right wing impacted the ground, and was substantially damaged, before the airplane came to rest. Examination of the right brake system following recovery of the airplane by a Federal Aviation Administration airworthiness inspector revealed that during brake pedal application, the right brake pedal went to the floor. Examination of the right brake master cylinder revealed no fluid. Visual examination of the cockpit area of the right brake pedal revealed no evidence of leaking fluid. The right brake was bled of air and the reservoir was filled with fluid. Visual examination of the right brake over the course of 1 week revealed fluid leaking at the slave cylinder. No determination was made as to the reason for the leaking slave cylinder. The airplane's last annual inspection was signed off as being completed on June 12, 2017. The airplane had accrued about 13 hours, and there had been no brake work done since the annual was completed. The pilot also indicated that there were no issues with the brakes on the flight into 2B3.